Purely removing shreck from volks would break the balance for another 6 months... I'm not saying it is a bad idea, just that it will take too much time to balance.
I believe the solution is on:
1- Adding munition cost to every single OKW abilities and increasing the low cost existent one to other faction level. This will reduce OKW overall powerfulness and force the player into tactical decision making around munition usage.
2- Add a fuel cost (around 10-20 each) to unlock shreck and flamnade + add a fuel cost (5) to the Kubel
3- Add a fuel/munition cost to the OKW T3 canon in a form of an upgrade.
4- Add a fuel/munition cost to the forwarded retreat point upgrade (and reduce its manpower cost)
5- Reduce manpower cost of doctrinal call-in and add munition upgrades (falls,jaegers)
While I voted for the removal of Schreks from Volks completely, I have to admit these are pretty good suggestions and Relic should experiment with them.