Alright. I read the first post only, and would like to throw in some points.
The ideas are basically great... which basically are one approach to solve the issue. The goal is to have much free room within the ship without the need to fill it. On bigger ships, 5-10% system blocks is a good ratio to have, to allow vast space for interior, or at least the option to modify the ratios or the setup of the system blocks. This would also allow system blocks to be clustered, and would allow them to be adjusted, as a certain order can be kept.
There is no real need to go for heat instead of energy. Heat is, as far as I understand, basically just [100% - Energy%]. The concept of having energy as it is makes more sense.
My proposal:
The ship's dimensions define what the average size of a system cluster should be. If the dimension value (result of a formula, be it x+y+z or with exponents involved) is 100, 10 blocks of energy generators/engines/shield blocks would be "normal" sized. Now relative to that ratio (50-200%, in this case 5-20 blocks) system blocks can be placed in order to alter their functionality with advantages and disadvantages. It is well enough if that only applies to energy generators, while every other system block interacts with energy, causing a natural limitation of how they can be used. Using too big of all system components will drain energy way too much whenever it moves, fires, regenerates shields, warps, etc - besides having the disadvantage of having a surplus of mass and negating the advantage large thrusters would offer straight away.
Examples:
Thruster:
Smaller (less blocks than the average): Less thrust, less mobility, lower max-speed, less energy consumption.
Bigger (more blocks than the average): More thrust, more mobility, higher max -speed, more energy consumption (both passively and when used).
Separating: Increases mobility generally, additionally increases mobility in the axis of their relative position, lower thrust, lower max-speed, higher acceleration.
Shields:
Smaller: Less shield capacity, less (relative!) regeneration, less energy consumption.
Bigger: More shield capacity, more (relative!) regeneration, more energy consumption (both passively and actively).
Separating: Less regeneration, more capacity (but energy consumption stays equal).
Generator:
Smaller: Less energy generation, less energy capacity, lower volatility (up to the point of barely having explosions), bonus on all other systems.
Bigger: More energy generation, more energy capacity, higher volatility (bigger explosion if taking enough damage, and relatively less damage needed to do so), penalty on all other systems (the systems which in turn use more energy (by being larger for example) will be exceptionally powerful and compensate the penalty of course).
Separated: Lower volatility, less energy generation, more energy capacity.
-> Beware! Only generators depend on ship size dimensions, and cause a modifier to other systems based on it and their size. All other blocks will have normally scaling, mostly linear values. Having 1 block of a generator only will cause huge modifiers, but having 1 block of a cannon will merely make it barely useful while barely draining energy, because it is simply not enough.
Warp (requires minimum block amount relative to ship size/mass to work at all - for every cluster!):
Smaller: Shorter jump distances, shorter charge time, lower energy requirement, lower mass.
Bigger: Much longer jump distances, longer charge time, higher energy requirement, higher mass (significantly increases inertia).
Separated: Safer jump in combat (assuming it would be delayed or aborted in combat), shorter charge time, higher energy requirement.
Weapons (generally):
Smaller: Less damage, smaller projectiles/beams, more punctual damage, higher cadence, lower energy consumption (more energy efficient), lower range.
Bigger: More damage (or rather DPS), bigger projectiles/beams, higher AoE, more piercing (damaging blocks as traveling forward), lower cadence, higher energy consumption (less energy efficient (less damage per energy used)), higher range.
Separated: No effect - would basically gain its effect naturally by having the advantages and disadvantages of multiple smaller clusters.
-> There needs to be a reason not to simply build in all types of weapons, as there would be enough space to do so. However, a good variety should also be supported. Giving them a good mass, passive energy consumption might be the way - but only beginning from a certain relative amount. Having too much options/variety should come at a price.
Scanner:
Smaller: Shorter range, shorter cooldown, lower energy consumption, lower mass.
Bigger: Higher range, higher cooldown, higher energy consumption, higher mass.
Separated: No effect. It only uses the biggest cluster.
Stealth (requires minimum block amount relative to ship size/mass to work at all) (integrated radar jammer! no reason to separate them):
Smaller: Increases energy consumption while active, less passive energy generation decrease, lower mass.
Bigger: Reduces energy consumption while active, passively reduces energy generation, higher mass.
Separated: No effect. It only uses the biggest cluster.
On the side of ship design, there are no good reasons to put too many of any blocks into the ship, as they will not work any more, or become too ineffective as they will consume too much energy. Energy generators are however always a choice - having too many of them will impose massive penalties on all systems, rendering even the specialized modules useless - having too few of them will make any/most other system unusable. The average (recommended amount based on ship size dimensions or mass) is the usual way to go.
This should free up a lot of space and order as intended, and give structure and a way to balance things properly.
Also, additional variations by different block types:
Energy generation blocks:
Block A (*insert clever name here*): Regular and constant energy generation.
Block B: Increases energy regeneration at higher current status, but lowers energy regeneration at lower current status. Best if keeping energy high at all times. Alternative to Block A.
Block C: Increases energy regeneration at lower current status, but lowers energy regeneration at higher current status. Best if keeping energy low, around 25-50%. Energy regeneration however drops down below 25%. Alternative to Block A and B.
Module* A: Allows energy to be used to absorb a part of shield damage taken.
Module B: Allows energy to be used to absorb a part of block damage taken.
Module C: Allows energy to be used to improve weapons, using more with higher current energy status. Best if firing when energy is high. But reduces general weapon efficiency, rendering them less efficient when firing while energy is below 50%.
*Modules: Are used as a modifier to the main clusters. Maybe one is enough, just like the computer blocks?
Thruster blocks:
Block A: Regular thruster.
Block B: Lower max speed, higher mobility. Uses more energy while turning beyond standard speed. Alternative to Block A.
Block C: Higher max speed, lower mobility. Uses more energy while approaching higher max speed. Alternative to Block A and B.
Module A: Combines warp module with thrusters, replacing warp by activating warp boosters, granting extreme traveling speed if activated. While active, turning speed is minimal, energy and shield regenerations are reduced, firing weapons is not possible.
Cannon blocks:
Block A: Regular cannon.
Block B: Rapid fire cannon. High cadence, lowest DPS, low energy consumption over time, high hitting rate (fast projectiles), low range.
Block C: Blaster cannon: Medium cadence, medium DPS, medium energy consumption over time, moderate hitting rate, some AoE, medium range.
Block D: Slow fire cannon: Low cadence, highest DPS, highest energy consumption over time, low hitting rate (slow projectiles), large AoE, long range.
Module A: Siege Module: Allows thruster energy to be redirected in order to boost cannons, improving DPS, hitting rate and AoE. The ship cannot use engines while active. Also causes the ship to stop slowly.
Module B: Burst Module: Allows firing in quick bursts, increasing cadence (or instead damage if it is too quick already) and with it DPS significantly, but rendering the weapon to require a cooldown.