Could multisig functionality be added to the GUI in a Privacy Mode worker proposal for a reasonable increase in the cost and without drastically affecting eta?
The blockchain technically supports using confidential transfers with multi-sig as well as with public accounts (keeping the amounts private). Exposing that in the GUI is non trivial. I would be very interested in getting some ideas of what that might look like. At this point in time though, I do not wish to increase the scope of the basic worker proposal because it is already tightly budgeted and we absorb all of the risk for cost overruns.
We would need "off line" signing of transactions and general multisig support throughout the whole wallet.
I would probably put off-line signing support as a separate worker proposal because its use case applies to everything the wallet can do, not just confidential transfers.