We could make like the ClashCon. You don't use your own base the game would give you a:
TH10 High(Or Maxed)...TH10 High
TH10 Mid....................... TH10 Mid
TH10 Low......................TH9 High
TH9 High(Or Maxed) ....TH9 Mid
TH9 Mid........................TH8 High
Two possibilities.
-Like that even TH3 villages in this kind of clan war could try the troops that they don't have.
-The match making would be fast because they are the same weight of war.
-The leader or co-leader obviously chooses 5 people of their clan and they select the TH of each member.
-It would be good that you could make your troops instantly in this kind of war.(You make them at the war base)
-This would be a different clan war. (Another Button)
-You would have a different Clan Castle to use your Reinforcement Troops.(Maybe a "5Vs5 Chat" because I don't know how to do different requests(Like a normal request for war and multi-player it would not be the same as one for 5Vs5 War)
If you have some extra Ideas leave a comment. I would appreciate that this would be in a future update.