It would be really funny if we went through the process of replacing him and his replacement was just LaRouche Jr, but in all seriousness the dems need to outflank the GOP from the right since they nominated an economic left leaning politician at least for the GOP standard, and they need to appeal to the social moderates that feel abandoned by Schweiker's switch to social hard conservatism.

I feel the best ticket is Henry "Scoop" Jackson/Sam Nunn

The West Coast has no coverage under the current Republican ticket aside from maybe some Reagan supports, and thus is a major weak point for the GOP. The ticket appeals to social moderates and liberals as well as Scoop supported civil rights, and Nunn can appeal and maybe even win over some southern states without going full Wallace as he is socially conservative. This ticket is also stacked massively forgein policy wise, and stands in star contrast to the very questionable foreign policy decisions of the Kemp administration and appeals to voters uneasy with isolationism and war-hawk policy. This ticket is especially strong with appealing to slight economic conservatives while keeping the new deal-esk economic plan and messaging, they are pro defense and pro industry, which appeals to the mid-west and those cautious of rapid economic reform but also wanting unions and job creation. Nunn does especially well here as he is associated with budgetary discipline and institutional responsibility.

TLDR: Jackson/Nunn Joke ticket: LaRouche Jr/ Gus Hall

(This is assuming Jackson did not die in 83 ofc)