General Arma 3 40k Mod Information
1) Arma 3 is limited to certain playstyles. There is no melee combat in Arma 3. Any 'Melee' troops have to be simulated by using exclusively custom made extremely short range weapons.
2) At this stage of development 40k infantry content is limited to basic and light infantry (a tactical Space Marine is the heaviest Infantry type at present) Likely Eldar units will be the most basic.