Yea I think those could be monetized like publishing tools in a conventional vertical, but the open source requirement of dealing with Bitcoin tx excludes that.

I think inevitably these are more features than products, I've considered adding vaults to shockwallet just for my own use

justin_shocknet

bitcoin

Revenue model of wallets

brunenzio

Many of the wallets make it easier to do multisig (Blue, Liana, Bitcoin Safe, Nunchuk, Keeper, Specter, Sparrow) and some of them make it easier to interact with hardware signers. But even these features are difficult to monetize, imo. 

Monetizing services can lead to situations like Theya, which seems now to be going hard into selling people a bitcoin loan collateralized with their house (Horizon).

I'm hopeful that the lightning wallets find monetizing more straightforward.