The 'chaplain' is in no way only a chaplain. EVERY centruion can take power weapons and plasma pistols

to make him a
MOS,
AT MOST take a paper clip and convert it into an antenna.
the,
IMO, 'best' way to build a single calth kit is:
1 Praetor (either model)
1 centurion (either model. In your case is gonna be a
MOS)
2 15-man tacitcal squads (In your case, can also be reavers)
5 cataphractii terminators (In your case, can also be justaerin w/ fists (OR claws if they can't take fists)
1 contemptor w/ kheres+fist
from there, you have an infinite number of ways to expand and are not forced to play the (terrible) Pride of the Legion.