get every hugely popular boom megawad or zdoom level set so long as the zdoom levels work as standalone levels without too much breakingconvert everything to hexen in zdoom format (because udmf is too large, and need scripting)
change all the level exits to call a script instead
based upon server cvar the script can either just take you to a random level or use a "random shuffle" which is where it takes you to a random level out of a set of levels that has been categorized based upon enemies and what weapons you get (basically progression) rather than level number, uses pistol start option's schtick
maps07 and 32 would have special scripts inserted into them for compatibility
probably end up with something on the order of 500 levels, maybe more
there would be a modified version of pistol start options included in the zip

downside:
this would be hugely in violation of "do not modify" clauses attached to most of those levels