My actual suggestions.

As I already made a thread for general development tips, I decided(just now) to make a thread for actual suggestions.

Raming blocks:

The name mostly speaks for itself, a block that highly resistant to collisions, but is otherwise not very effective as armoring. It would generally be used for things like boarding pods, or on the bottom of dropships so that they can spend less time trying to slow down while landing and more time dropping troops off.

Custom(ish) weapons:

A make-it-yourself person's weapon. While normal weapons such as railguns and lasers and such are fixed, and usually made out of a single or multiple blocks, custom weapons are made out of several different blocks that can be stacked together and arranged to fit whatever ship it's on and the desired power of the weapon.

As a example, lets take a custom laser, there would be emitter blocks and vacuum tube blocks. The emitter blocks would emit a weak, low powered laser either into the air, or into a vacuum tube block. While traveling through air, lasers would reduce in strength according to the distance traveled and the intensity of the laser, but while traveling through vacuum tube blocks it would have ether no, or nearly no loss. The tubing can form corners and junctions, and it would evenly split the laser's power between all connecting tubes when it meets a junction, and visa versa. This could allow for a variety of things, like spreading out the emitter blocks over a ship for redundancy and strength, but in turn every time one of the diodes is destroyed it reduces the strength.

That system could be adapted to other weapon types as well, railgun tubes could require constant power and increase the strength for every block the shot travels through but reduce it for corners.

Custom controls:

How you could go about this varies, you could just allow remapping of the direction keys for ships, or you could have something as complex as a mini-computer(like what Eloram's working on) to control individual thruster blocks. The main reason this would be useful is when making unorthodox ships, like a UFO, instead of something with a definite back and front.

I'll post more as I think of them.