If credits could only buy blocks, they would become worthless, as everyone would want blocks but not credits,
Why, exactly? Blocks are situational, credits are a universal expression of value, and would still fill an important role. I'd say it's no more a risk than everyone in a real-world economy suddenly investing everything they have in gold.
and then nobody could afford anything until they started salvaging again
Why would they need to afford it, this scenario only happened because they already bought it, right? Also, the shop system was never intended for mass production of items, that's why we have factories.
Nobody would start salvaging to sell because all the shops will be out of blocks and/or money (Rapidly inflating the player market). [...] Thus only factories could help, but many people don't use factories as far as I've seen.
Well, that's because they've never needed to. In this scenario, they will.
Credits would not be universal if they were only used in shops, and currency in a video game that has almost no use (Since all the shops are empty or broke, or both) causes massive problems.
Like I said, they're a universal expression of value, not a universal tool. The purpose of credits is to have a common denominator, a base unit if you will, that the economy can use as a starting ground for comparing and exchanging resources.
Again, from where did you get the idea that shops should be the primary source of recourses? They're a mechanic implemented as a practicality for smaller parties with no comprehensive infrastructure, not as the source from which all materials derive. That's what manufacturing is for. If manufacturing it to inefficient for such a purpose, then again it's the factories we need to look at, not the blueprints.
If factories gained enough of a boost to counter this, then they would be overpowered.
How? If something receives well-wieghted buff to reduce an imbalance, and does this successfully, how can that make it overpowered. I do fail to see your reasoning here.
Configs are a great possibility in controversial topics like this.
Indeed they are. In fact, it's getting increasingly obvious this is just a matter of personal preference, not a flaw in reasoning on either side.
If players could steal ships while they're being built it would cause large amounts of frustration on multi-player; therefore you shouldn't be able to undock a ship from a shipyard while it's being built.
Yes, that seems reasonable.
If players could ask the shipyard to start building a ship before the shipyard has all the blocks needed, then players could easily jam the shipyard making it impossible for any other players to use the shipyard - e.g. a partially built ship that can't be undocked until it's finished, that is never finished because the shipyard is waiting for the other blocks. Therefore, the shipyard shouldn't start building until all blocks are provided by the player or the shop (so that completion can be guaranteed and "permanently blocked shipyard" can't happen).
It's an issue, but a rather easily fixed one. The "constructor beams" I suggested would mean there's no actual yard to occupy, and the beams could easily just ignore the first ship they were building and work on a second one in the meantime.
The problem with using blocks is that there are too many different types of blocks. For example, just looking at hulls alone, there's normal and hardened, 8 colours and 5 shapes. That adds up to 2*8*5 = 80 types of blocks. In total, currently there's over 400 different block types in the game (and it's likely that the number of block types will increase in future).
Not every ship/blueprint uses every type of block. However, especially for ships that look awesome (e.g. detailed interiors, etc) it's easy for a ship/blueprint to use more different types of blocks than a player's inventory can hold. If you actually have all the different blocks you need, you couldn't carry them to the shipyard in one go.
Ever heard of plexstorages? They all link to the ship's central inventory now, so you could accommodate as many block types as you want. Besides, it's unlikely to be an issue in the first place, as shop-based construction systems are intended for smaller ships.
It also means massive hassle. Just trying to figure out how many of which blocks you need to collect before you go to the shipyard would be a major headache;
Not if the game did that counting for you. A rather simple GUI feature, I say.
and if you've got 9999 of the blocks you need except that you're missing one blue hull wedge (and the shop is out of stock) and only have 99 spare blue hulls that aren't wedges then it'd suck.
Then you'd have to manually add that one block later, the shop could build the rest of the ship for you.
To fix all of this; instead of using blocks you can use the ingredients that make blocks. A player's inventory holds a max. of 45 different types of blocks. If there were no more than 45 raw ingredients that can be used to make all blocks, then you could collect all the ingredients, then head to the shipyard, select the blueprint you want, unload everything and press "go".
Note that I'm mostly worried about new players who are struggling to gather resources - e.g. the typical player that's just joined a server for the first time; is trying their best not to get wiped out by pirates; has no station, no factory, no home base, and only has 1 ship core, 1 weapon computer, 14 thrusters, etc to work with. Most of the problems don't effect (e.g.) large established factions that have a massive stockpile of resources, their own factories and several of their own huge shipyards.
Since your mechanic would still require players to have the raw materials, it seems the issue we're really trying to solve (Aside from a few easily-mitigated hassles, as discussed above) is that the factory system isn't open enough to new players. That might very well be true, but as I keep saying, then how about we fix the factory system instead of buffing everything else to compensate?
How about shops offering fairly efficient and automated crafting at a small credit price? Or maybe allowing a few factories on every ship? There are a lot of possibilities to look into, but I don't think this particular tweak to the shipyard system is one of them.