If we were to actually do 6 draft leagues together, it can't just be a random assortment of leagues. They either have to be iconic leagues (ODL, $52M), challenging leagues (autodraft, no all-star all-stars, albatross, some sort of banned league), or a franchise league of some kind. We could even have 6 different commissioners to spread the work load around.
I would vote for the following 6 leagues:
ODL
$52M
Autodraft
Either no All-Star All-Stars or albatross (Not both)
Some sort of a franchise league (Twist or no twist)
Banned league (Maybe no players drafted in the ODL or $52)
This gives us the classic low and high cap leagues (ODL and $52M), a unique league that was beloved (autodraft), a league with limited rosters (NASAL or albatross), a franchise league, and a banned league.