Good ideas, but I think they might overshadow Volley Fire/ HMG and grenades.
Personally I think BARs should just give greater firepower boost to make them a worthwhile investment, sort of like adding LMG42/34 to Grens/ Obers. Not as much if you just had one, but if you fill both slots you make your Riflemen/ RETs unable to deal with vehicles.
The Bazooka ability could instead be used against vehicles, to slow them down and give slight stun, would be a hybrid of Button and TWP. Seeing as it's already munitions ability on top of 60-120 munitions just to buy the bazookas, I think this doesn't make it close to panzerschreck but allow for more useful strategies against vehicles besides human wave salute for Old Glory suicide runs
I said that RE's would lose volley fire in order for the BAR's to provide it. Volley fire is kind of crap with the horrid received accuracy debuff RE's receive while using it. As for your other points, you must realize that all this would cost a decent amount of munitions, thus making it difficult to spam without investment into muni chaches. The BAR ability would be meant as a stopgap if you don't have the .50 unlocked and the WP 'zook round will help if you don't have indirect. As for replacing grenades, I doubt it since you have to sit in WP for it to do damage. It's more of a building/cover denial similar to Soviet Molotovs
The 'zook stun is kind of unnecessary because rifleman smoke grenades can stun vehicles.
Again, this is all just my opinion, but BAR's were nerfed in the first place because when USF came out because they had tremendous firepower (they use the assault rifle rather than the lmg profile) that would overpower just about everything. I hope to steer away from that and let them provide more utility.