I think Durable, Skirmisher, Charge and Banish will all need to be reworked a lot for this. The names probably will need changing as they will make little sense in their new uses.
For example,
Durable: Cards stays on hand, discards Skirmisher
Skirmisher: [an effect of some sort], discards Charge.
Charge(N): Same as now + Discards Durable
(Banish: Banished into non existence.)
Of course, it doesn't have to be just 3 keywords that do this, but adding much more will quickly make it complicated.
The Keywords can also be thematically given to cards (sort of like they are now), so for example, Defensive structures might be Durable, Soldiers may have lots of Charge cards, there might not be any Undead Charge at all! Or all Undead Charge cards would be quite weak in other ways.
This would create the need to either be very vulnerable to other kinds of decks, choose some of the said weaker cards into the deck, or have more cards from outside the decks scope.
Obviously, the keyword effects above are just examples and probably need a lot of tweaking and reworking before this is worthwhile, but it would really add a lot more flavour especially to the most mundane cards in the game. More cards would be able to discard, and be discarded by simple cards.