decentralized wallets and payment processors

I've been sketching out an implementation of a payment processor and wallet
system lately

Turns out decentralized wallets are a really hard problem to solve

Some thoughts I had:

1. A multi user wallet, seems to be roughly the same thing as a payment
processor, when in a decentralized environment

2. A decentralized payment wallet / payment processor should be able to
largely live in the browser

Note: I'm looking at this from the perspective of crypto currencies to
start with.  Fiat may require more thought / work.

Some questions:

Would these two goals be desirable to the group, because it's what I'm
trying to create?

Are there any technical barriers why this would be impossible using web
technology?

Or is it out of scope for this version?