yeah, i was actually going to modify some of the ufopeadia text to give useful information on alien vulnerabilities because of what i'm doing to armour/resistances, and give a small damage boost or something against a race that you HAVE researched (basically analogous to researching in system shock 2)
as for the motion sensors, i like where you're going with this. i'm thinking that for each LIVE alien species you research, it allows for differentiation of that species' blob, not sure how i'd handle this for proxies.
shaped explosions: yes, yes and more yes. claymores, breaching charges, all that good stuff.
i'll be messing around with the tech trees too, i want power armour to be a branch of muton research and flying armour to come from floaters and ethereals - floaters for propulsion, and ethereals for the alien nano-weave (their robes). you already gain sectopod construction from sectopod research.
multiple ammo types for HWPs will be a simple addition, i'll just have it as a different fire mode, ie: aimed shot becomes AP shot, snap shot becomes HE shot, auto shot becomes IN shot (single bullet of course) and as an added bonus, i'm gonna have a coaxial machine gun in the "left hand" slot.
thanks for the suggestions!