From @meshcollider:
We now have essentially the same code in the bumpfee RPC, in the GUI when drafting a transaction, and now here when bumping in the GUI too. It would be nice to consolidate it a bit. If you want to leave it to a follow-up though I am happy to merge this with the current ACKs.
From @promag:
bumpFee should not be in the wallet model - could follow same approach as WalletControllerActivity - because IMO it's wrong to open message boxes (any GUI change) or copy to clipboard from a model class;
bumpFee should be asynchronous - 1. above would help here - if from the GUI thread we hit cs_main or cs_wallet then that's bad;
we keep adding nested event loops with QMessageBox helper functions - again 1. would help here.