Concrete blocks, not concrete voxels
I know this idea has been declined and this is sort of duplicate of https://support.keenswh.com/spaceengineers/publictest/topic/a-use-for-all-that-gravel-concrete but please before declining this, consider it in it's most simple form. It would provide a lot of benefits with very little work.
I really fail to see the complexity in concrete blocks since they would basically be reskinned versions of armor blocks with a bit different stats, usable only in large grids, unless there are some underlaying issues. There are many great ideas how they could work, and I'm not claiming any of these ideas as my own.
A) Why concrete blocks would be great addition to the game:
1. They would encourage people to actually build beautiful bases as steel plates are always needed for everything and there are more important uses for steel plates than wasting them on enclosed buildings, but gravel just piles up.
2. Cool looking bases are a great way to showcase this game, much better than a platforms of steel frames everywhere.
3. Base building encourages creativity while freeing up resources for ships.
4. Players like to do something while waiting assembler to produce more components or refinery to refine more ore. Working on base can be very nice time sink, but with limited steel resources required for everything, people are just waiting next to assembler or refinery.
1. Large grid blocks only.
2. Make concrete blocks so heavy that they would be impractical on ships while less durable than normal armor blocks.
3. Armor blocks would be basically improvement over concrete blocks adding a bit more progression.
C) Construction & components:
1a. Refine X ammount of gravel into X ammount of concrete bags, fast process.
1b. Concrete blocks would need X ammount of girders (for example) and X ammount of concrete bags (As just an idea, 1 girder 10 concrete bags).
1c. Or concrete blocks could only need concrete bags.
2. Or to make it even more simple and easy to implement, concrete blocks would only need gravel to build.
3. Concrete blocks would be fast to weld (no need to nitpick about welding concrete blocks please, it's a game).
4. Three construction stages. Stage 1: Frame, Stage 2: Filled block, Stage 3: Complete block.
5. Grind down into gravel.