I think, it’s very difficult to find all cards which are good in combination with, for example soldier, because there are cards like Battle formations. So you have to search for such cards, but often you don’t know the name of these cards, than it’s very uncomfortably to look for it.
A filter which makes it easier to find such cards would be the “combo-filter”
It shows every card, where the keyword you can choose plays an important part.
I hope you understand and like my idea!