This is one approach, but it fails to account for of what the mass of this ship is composed. You could have a ship that has no guns because it focuses on shields and warp-drive, another that is practically nothing but missile, and another that has a dozen turrets each with a different weapon/effect combination, but all of these having equal mass.
If you only consider mass, you fail to account for how combat-effective the ships will be. Other traits like cloaking, acceleration/turn speed, energy recharge, etc. can also affect the ships difficulty. Then we have to consider which is harder: 1 ship with 5,000 shield and 100 dps or 2 ships that are each 2,500 shield and 50 dps, or 3 ships... etc. Then we have to consider how the weapon systems are arranged - does it shoot 1 missile that does 1,000 damage or 100 missiles that do 10 damage (and are harder to shoot down/avoid). Is the cannon system a single laser or a checker-board array that is harder to dodge? Does the ship have multiple systems and if so which one is considered the primary weapon? Does the ship have effect modules that boost speed/damage/defense, and will that give it an advantage against the player's ship's effect modules?
Lastly, how will the AI's aim and maneuvering affect the effectiveness of all these systems?
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I'm not trying to shoot the suggestion down. I really do want something like this in the game and feel it is vital to balance and game progression, but it is a bit more complicated than it might at first appear.
although you are right with the count system, it doesn't need to be like that.
when you are owner of a popular server, you want to keep it that way or let it grow.
if you make ugly waves of cubes full with only needed things it will bring your server down.
nobody likes way to hard waves and ugly ones.
when we put the mass max on (for example) 1k,
the maximal attack modules the wave can have is 1k modules.
but the server owner wants to make it pretty and working (so power and shields)
this makes it a wave would only have 100-500 dmg modules.
we don't need to decide what is stronger. more mass means more blocks means stronger.
this is correct in any way. if you cross the limit of 1k it will be stronger as it has more blocks.
the server owner will find a compromise between an op easy wave and a way to simple easy wave.
i think there is no need for any hard formulas to calculate the hardness of a ship.
note that 1k was an example.
but if you really want a different ranking option i know 1.
we give every blocks a space ranking. this sounds weird but you'll get it soon.
a normal hull would be 1 SP (SP= space points)
the better hull would be 2 SP
and so on.
we could rank the weapons too.
cannon 5 SP
computers 0,1 SP
shields 5 SP
these numbers are examples though.
with this we can just set a maximal SP.
this idea is kinda simular to the mass but then with a bit of your comment ideas in it.
the ranking of the blocks can be done easy, look at the normal wave of pirates atm.
rank that so it looks logic. take multiple ships and look what their average SP would be.
then when we know the average SP of medium ship we devide it in what an average ship contains of.
so we first say max will be 10k SP
then we check the ship.
we want to devide every sort block in a way that it ends in 10k SP
that ship contains 1k armour. we give every armour block 1 SP
it has 1k shields (also reg) it has 1k power and 1k damage things.
we want to devide 9k into 3k but unequal.
i think power is less important lets give that 2SP each block
7k into 2k
shields are very importand so are dmg modules.
3 SP to shields
4k into 1k
4 SP to dmg modules
this is how it would be done