Oh ur right... Well... Maybe OITC?
OITC requires a plugin. It can't be run off self-regenerating command blocks like something as simple as spleef (and by spleef, I mean more along the lines of Runner, no-shovel-whatever spleef). Also, OITC would require PVP being disabled, bows being given to the players in lobby (which would start people being shot out of the hub and forcing that to be patched...again).
I'd be more inclined to just let donors join the staff in being able to fly around lobby or something simpler. Minigames in the hub wouldn't lag as much necessarily - anymore than the hub already lags - but something as simple as Runner would do nicely. The only bit of lag that you might experience would be when all players were off of the "course" and the command blocks would be spawning in the new blocks. In addition, the way to combat the problem of players being unable to fly out from beneath the spleef/runner arena would be to disguise command blocks as barrier blocks down beneath the Runner area to TP the players that fall back up to the starting area.