the fastest car around tracks would look like red bull x2014. in that hypothetical world, the most important variable is aerodynamic efficiency, which is highly restricted in today's f1 regulations, but not so in lmp1. Plus, hybrid units are much more limited in f1 than lmp1:
4mj of energy through 160hp motor per lap as opposed to 8mj through unlimited power motor for the porsche. Moreover, there is a further bottleneck in the energy stored per lap in f1. Combustion engines are more powerful in f1, but this is irrelevant as total power allowed is higher for porsche lmp1.
"The ultimate fastest car would look a lot more like an LMP Car design than an F1 Car. Closed cockpit, closed wheel, AWD, larger battery output." This is just because f1 rules are much more restrictive in aerodynamics. i am not sure about 4wd, probably not, as in current tracks downforce will be much more important than mechanical grip at those theoretical speeds.