Mugen Field and Level Caps

[DigoleBicks]

Quick question if anyone has any idea -- I've not raised any of my story characters above level 1000,  syrma and our previous superhero from the last game (subtle spoiler whatever) are 500, etc etc. However I've raised the level of a few peons up to around 7000 on the way to 9999 to begin swapping some stats... But before I do that, since i've heard Mugen Field increases in difficulty (in what way? just beefier foolmans?  and by how much?)  i was wondering if, say, the 9999 peons made it uncomfortable -- if i sat them out of the party and sub party or released them, would the Mugen Field difficulty return to my party's normal?  ( 500, 500 , 1000, 1000 and weaker characters on the bench)?

Also i have increased my Bet to 5 million (1 less than max) and i know that has some effect as well.  Any data / anecdotes would be appreciated broz