The challenge, with a POD no earlier than 1400, is to get a member of the French Royal line in the Throne of the Empire. They don't have to be kings of France but they must be a legitimate prince of the blood.
My first guess would be the Burgundians- IIRC they had some ties to the Luxemburgs, if the Habsburgs go extinct in the 15th century them they might be able to secure election through a mix of bribes and marriages. Another alternative is the Anjou, either the direct Capetians or the Valois spinoff, being more succesful, keeping Naples and Hungary and springboarding onto the throne of Bohemia and there to the Imperial title. Francis I did seek the throne but Charles is too rich, too powerful and too well entrenched, the Habsburgs and Luxemburg need to be weakened enough to remove them from the running (the Habsburgs stating divided and not getting Spwin/the Low Countries/Milan/Hungary).