Seems to me like all we really need is Off-hand Sneak Attack ...
And aply SA to AoO, since that is happening outside our turn, so we would not loss any resource ... and therrfore there is little to no reason to not aply that.
This doesn't solve the entire problem. I think you're suggesting that we have dedicated icons for BOTH a normal sneak attack and bonus action sneak attack, correct?
First of all, it is inefficient when you're attacking the same enemy. Attempting (and missing) with your normal sneak attack, then attempting an off-hand sneak attack requires 4 clicks. Click the icon -> click the target -> click the BA icon -> click the target. Whereas, with a toggle, it requires 1 click: click target (with the "attack with both held weapons simultaneously" toggled on.)
Second of all, it exacerbates the problem of hotbar-real estate by needlessly adding another icon. Now sneak attack takes up 2 icons.
Thirdly, it runs into a multiattack problem: if your rogue has two main-hand attacks (from haste or multiclassing), they'll still only be able to sneak attack on one of them and if they miss they get no sneak attack damage.
Finally, and perhaps most importantly, it still doesn't work with special attack-action abilities gotten from multiclassing, special ammunition, etc. Since you can only click one icon for an attack, you'd
either be able to sneak attack or use that ability when you
should be able to do both. E.g., a rogue-battlemaster figher wouldn't be able to sneak attack + menacing attack at the same time.
