20% is fine early game, but you have to consider RE only deal damage through their gun upgrades. They also have worse survivability than Rifles and lack grenades along with snare. Rifles also have 30% weapon accuracy when they get to level 3 on top of another hit of RA.
They only can get 1 weapon and a sweeper now from the 2 weapons with a sweeper. Unlike the other engineers, RE generally don't do as much building or support due to vehicle crews so they'll be fighting more.
Do note RE were never worth 200 and Volley-Fire only had one use and that was against Ostheer pioneers who decided to close the gap at max range rather than backing away when the ability activates.
Besides, I think people would prefer not having to go Rifle, Rifle, Rifle every game to hold ground outside of certain strategies which intentionally avoid fighting until an officer arrives.
If the base line is EFA, R.E. are far more cost efficient than Pios (cost 200) and CE (cost 170).
In addition currently a bar or LMG is better in the hands of RE since they get 20% accuracy from vet 1 something already fixed in Conscripts and Ostruppen with accuracy penalties (even thou these units have limited access to weapons).
If you do not want to use the same penalties at least replace x120% accuracy bonus with "volley fire" as a vet 1 ability.
Making a unit OP to diversify built have proven disastrous (like the Penal buff), each units should have a role, bring utility to table and not simply be OP. So instead of turning them into riflemen baby brother give the a role or move some of doctrinal abilities to them instead of riflemen (field defenses, Forward observes, smoke grenades...)
Cheap Rear echelon where tested and found OP so they had to be changed:
DECEMBER 3 UPDATE
"Rear Echelons
We have scaled up Rear echelons up slightly to reduce spam.
Rear echelons cost up from 160 to 200
Rear echelon rifle damage up from 8 to 10"
If one want to further avoid the riflemen, riflemen, riflemen built one should consider a promote system where USF units can be promoted to officers and elite units.