I'd prefer the AT-XT from the Clone Wars game, where it first appeared, and it's a tad smaller in height I believe. Not that the drawings there are bad, they just imply a height greather than what the game's original design showed. Taller than an AT-ST would be I believe, and this was the AT-ST's actual predecessor (not the AT-AP, or AT-RT, or AT-PT, or anything else... 2 legs does not equate evolution here).
As far as just a new cab on the AT-ST, I disagree there as well... Not going into the fact the AT-ST's way short, there's a ton of differences in them I see visually that would make a simple cab retooling unsatisfactory to me. Right off the bat the feet aren't the same between the two... LEgs are much thinner on the XT too, though the "hip" joint arm looks to be similar. The drive section seems to be built to the cab as well, and all of them seem to move somehow. Just looking at that... That or the cab is stationary and doesn't pivot. I don't recall how it worked in the CW game now off-hand.