I hope Grens and PG can build wire and sandbag (not the stupid crap now we have that requires to be build for ages) once more, it's the best thing I can recall from COH1 wehr
I'm okay with wire being restricted to Pioneers, it makes sense that they'd be the ones handling it the wire. I do think it is odd though that Grenadiers (and conscripts, and pretty much any regular infantry) can't fill a sack with dirt and stack it, though.
I wouldn't be opposed to a 'preset' sandbag wall, like what the conscripts can build. People are probably going to hop in and say "but Ost can build bunkers". Yes, but bunkers cost manpower, piles of dirt are free.