I think the toughest part will be finding a shop that will mount them up for you. I was told by my local shop that bindings have to go through a quality test before they can mount them, and if the binding doesn't pass, they become liable. I don't know what a mismatched toe piece will do as far as that goes, but it might give the shop some problems when it comes to fitting on the jig.
With that being said, I've had some pretty janky bindings mounted that definitely did not pass the test. Usually it just takes the help of a pizza or a 6-pack along with your word saying that you won't sue them if you mangle yourself up.
I say go for it.