I don't see why you should ban "combo" cards and "fix" culture-less cards. You basically kill deck desing by doing this, discouraging combo decks and rainbow decks (or rainbow splashes, which is ALSO deck design, since it makes deckbuilders check out ALL the cards when building a deck, to see if something outside that particular culture might stand out as useful.
Actually, combo decks are strongly against the point of LotR. Card combinations can be fun, but the horn deck is just flat-out overpowered. Its like a site 1 win against any skirmish oriented deck, and sets up a mean shadow kill. There is no counter to the Horn combo, except maybe
A Dark Shape Sprang on Gamling with expanded Gollum cards...but nobody's playing expanded Horn, its all standard.
The deck CAN be killed, but I'm just saying you cannot stop the combo from going off, and it leaves swarm shadows virtually unstoppable.
As for rainbow splashes, they're fine, but just a 0 twilight card that completely freezes something...let's just make sure they're at least playing a hobbit in there.
I have a rainbow deck, actually, built on cards with hefty spotting requirements, like
Glimpse of Fate,
Brooding on Tomorrow,
A Light In His Mind and
Hardy Garrison. It runs ALL of them. And works well with the spotting requirements. plus, it runs some specialized possessions, etc. Cultural enforcement doesn't mean no rainbow decks. It just means Shire cards aren't being run without a hobbit.