Keep how it is now.
Allow elixir to upgrade any level walls.
Is it a money-back guarantee?
I say no, and I'm a TH7 upgrading to TH8 (I'm starting the upgrade tonight). My alt accounts are TH6 currently upgrading to TH7, and a defenseless TH5 about to upgrade to TH6. I have 3 accounts heading to TH8 in the next couple months, so I would benefit tremendously from elixir walls at TH8.
I still say no.
Personally, I think L9 walls should be gold-only as well. I'm on the fence about L10 and L11 walls. There's no endgame for elixir, other than building armies/spells.
Because it breaks the economy however you slice it...now town hall 10s probably will have a drought in the future due to town hall 9s dumping elixir into walls...PERSONALLY (it's in all caps because this next statement is my opinion) I feel like elixir walls only came out because supercell gave into whining about excess elixir in the first place..I understand wanting new features or whatever but I never was happy with that update..couldve done something else like...I don't know...make it so that you can upgrade two things in the lab at a time instead of just one... that's my opinion though