One issue I see in most 4x space games I play is that aside from exploration ships, speed is often under-represented.

The main reason is space games tend to rely on fleets, which move at the speed of the lowest common denominator. So for a fleet to move fast, it must be comprised of all fast ships. Unfortunately, fast ships also tend to be less effective in weapons and armor, and so can't always do a lot once they get on site.

So the suggestion: Create a Fleet Speed, that is a weighted average of the speed and sizes of the ships they comprise (and then round up or down as appropriate). This means that a fast ship can increase the speed of the whole fleet (a warp bubble concept if you will).

Example:

Two size 1 ships (move of 8) + one size 2 ship (move of 4).

8*1 + 8*1 + 4*2 = 24. 24 / 4 size = 6. The fleet moves at 6.

So even though the faster ships can't make full use of their speed, its not completely wasted, and helps bring the big gun into the fight quicker.

This could be a midgame support module or engine module. IIRC, there was tech in ES1 that allowed a module to boost fleet speed.  There could be something like that again.