In a bid to try and rationalise things, my army (not including the Skitarii) has two distinct factions. The majority of the army comes from the Astra Militarum codex with some of the more specialist troops coming from the Adeptus Astartes codex so I thought I'd call the Tyranid hunters (Skitarii)Space Marine Scouts, just to tie them in with what I have rather than starting another faction just for a couple of squads. Here's what I have listed so far:
Astra Militarum:
HQ Squad
Infantry Platoons
Sentinel Squadrons
Weirdvane Psykers
Primaris Psykers
Engineseers
Priests
Ogryns/Bullgryns
Rough Riders
Vehicles (TBD)
Adeptus Astartes:
Terminator Captain (Exo Squat)
Terminator Squad (Exo Squats)
*NEW* Scout Squads (Skitarii/veteran Tyranid hunters)
Obviously, lots of it is WIP but I have managed to convert/sculpt over 80 so far so the army is slowly getting there