Pio's deserve to be a combat troop, not just a repair/building/capping unit. By giving them all these tasks you force the Ost player to make trade offs. Trade offs are good for the meta.
CE's don't need to be front line troops to be balanced. Their primary goal is to produce obstacles and mines. If you upgrade them with flames they are good at protecting supporting units. They force a different range of trade offs. CE's at range can deal some nice damage right now if they support another unit.
Both units should be equally viable in their roles. Pios can also get flamers as well to increase their DPS. CE and Pios are(were) the most mirrored units in the game. They build structures and mines, repair, harass, and are cheap. Best way to asymmetrically balance them is to raise Mosin DPS so CEs are effective in far ranges while Pio dominate in close ranges. As of this moment, stock Mosin DPS is really low to be effective...less than half of K98's DPS and a fraction of MP40s in close ranges. It's literally the weakest weapon in the game.