In theory you could do something like putting a rocket assisted 40mm grenade in a mk-19 automatic grenade launcher.
You would probably need to redesign it to shoot a longer round but I can’t think of why it wouldn’t be doable.
I suppose that would be closer to a full auto RPG at that point
GW has catered to scalpers for a while now; they won’t lose any sales. For a boycott to work you have to not buy from GW and not buy from shady resellers on eBay and do this long enough for the shady resellers to decide it’s not worth their money to preorder everything GW releases. Good luck with that.
Most people onboard with a boycott won’t think this through and they will buy stuff from resellers. GW doesn’t care, they already sold the product and made their money.