@Armorer
Hey.

Im not that good in balancing stuff, but my plan is to write down the stats and lore of the weapons already in the game, and compare them with the lore of the 40k weapons.
actual both, start with manned ones and later with the technology and some craftet machine spirits, unmanned ones.
Beside that i plan to give the turrets more an supporting role. The main combat should be between your soldiers, and the enemy.
Hrm.. good question. Will took for the tyranids a bit inspiration from the Rimbeast mod, but besides that like the weapons.
Nope no vehicles planned. Thing they do not fit that mutch in to the playstyle of rimworld.

A bit more than in the vanilla game, because there will be many meele based factions. So the player need something to "block" them.