Quest for the perfect deck (mixing decks)

[FireTigeris]

Did a search didn't find what I was looking for search terms 'mixing decks' so:

Ok, so when one gets a theme deck with a missing 'component' by design
(Oz as an example that plenty of class has no race) [again with the class joke?]

what's the best way in your experience to fix it?

I'd thought I'd ask you the experts.

As poorly balanced Munchkin games are not as fun and it's harder to have repeat players.

This thread is to avoid trying -every- possible permutation of these:

"Oh just add 'X' of each (type card)"
"Oh add 'Y' of each (type card) for each player"
"Oh huge decks are fun, just mix it in have 800+ cards between the doors and treasure + a theme- no problem...you don't want them out of there do you?"
"Oh we keep a deck separate that only has A,B,C cards in it so we can always draw one"

What do you suggest?

The best possible (IMHO) would be a pack of cards form Fantasy that could be quickly divided (if needed to not replicate the theme deck) and shuffled into any theme decks to add what's missing....but how many, how much?

EX>
players +1 = fantasy race,
players +1 = fantasy class,
players + 1 (or 2) = Player friendly NPCs- (hirelings/henchmunch/allies/mooks/comrades/monster bait/pack-mules-etc whatever you all them or whatever new ones surface),
players - 1 = cheat cards,
players - 1 = super munch and halfbreed,
# players = Monster adding/cloning cards (mate/wandering monster/dogpile)
# players = monster enhancers
# players = item enhancers
1/2 # players = continuous effect /no slot items (impressive title, Singing and Dancing sword)
1/2 # of players = combat removal potions (transferal, poylmorph, friend)
# players = Any type of die loaded/reloaded dice
1 = 1/3 breed or Chimera
1 = super duper or Ultra
1 = CWBH,
1 = Wishing (pill/ring...)
1 = item Enhancer enhancer
1 = monster Enhancer enhancer
1 = everybody is effected curses,
1 = everybody GUaL (I think I saw one once... but I may be misremembering)
0 = GUaL,
0 = 'regular' Curses,
0 = extra rides (horses, ships not included with that theme deck already)
4 = combat strength counters (one for the current combat player, one for any player helping using combat strength, one for the monster(s) one for the next player to get ready with)

If I get the 'formula' right I could sleeve/mark those differently so that can be pulled easy for the next theme game - like a mini fill out this theme deck.