Putting Kamala in a President would be the worst thing you could do if you wanted her to get elected in November.
Four months is both an eternity and nothing in presidential years. It's an eternity of time in that there are tons of chances for you to fuck up or something that's been cooking to blow up in your face, but no time to actually do anything you can campaign on. Kamala has also been kept in the back for all of Joe's presidency due to the fact she's so unlikable. The problem is this gives her no grand achievements that she can point to as VP. It would be very difficult to even manufacture a former achievement at this point.
Kamala already has next to nil chance of winning the Presidency under these conditions, but putting her in office, unless you've got some grand plan, would make it essentially impossible to win, even with massive fraud.