The main problem is that any change to the Puma risks bringing back the MobiDef meta, as the Puma fills a very crucial gap in Ostheer's line-up.
You said it yourself: “the Puma fills a very crucial gap in Ostheer's line-up”. As long as the Puma is doctrinal, this will never change. If doctrine is made viable again, then it will become a must have in your loadout (in 1v1), thus limiting your choices.
I propose that the puma is made non doctrinal with -10range nerf to prevent it from totally dominating other light tanks (non doctrinal smoke canisters could be added as a compensation)