Remove/reduce/pass around the extra 100mp they start with. The SwS is a good unit/tech requirement you could reduce mp wise so you would effectively keep the same overall teching cost.
About the SP as a unit, they had been hugely buff in the latest patches but outside of them getting a 5th man or weapon upgrade, they are not gonna be an infantry unit which can compete with main line upgraded infantry. On top of having plenty of roles.
I mean, this were the last year December changes:
While these may be "buffs", the only ones you ever notice is the reinforce time. It's rare to build a 2nd sturmpioneer unless its a heavy urban map, or you've lost yours. Vet 4 and 5 combat bonuses received nerfs and those are hardly obtainable anyways. Pop reduction is nice but when literally every other unit in the arsenal received a popcap increase it didn't matter. OKW now suffers heavily from its popcap lategame. The panzerschreck is just awful anyways. Paying 70 munis for potentially a 120 damage source and hampers the units AI which gets outmatched by midgame anyways unless you hit vet 2, which you then get about 2-5 extra minutes of effectivness until weapon upgrades put the unit on the sidelines completely. Not to mention lack of sweepers.
The unit simply is asked to do too much.
As said previously you'd need to rework the faction or the unit entirely because if you start with a volks OKW would get destroyed by UKF. That matchup currently can go either way, but it would swing to UKF entirely from a volks starter. Not to mention you'd then later have to build the SP which would make their vet even more unobtainable.