Gunship-hmmm...I guess...let's wait for the others' opinions.
Sniper/Ion trooper- Ion troopers are obvious in the movie but republic speeder bikes weren't even in it. I think both should be in but have different caracteristics.
To avoid giving the Republic too many anti-mech units, you could turn the AT-TE back to the simple all-purpose vehicle instead of an anti-mech.
As for snipers, they're hit-and-fade sneek around units, something that the Republic obviously isn't specialized in(taken in the context that the ARC trooper doesn't exist).