Some colleagues and I are running into a bit of a problem. We've been using RFC 1918 Class A space but due to the way subnets have been allocated we are pondering the use of public IP space.
What you are suggesting is unacceptable. You need to allocate your private space more efficiently. It should be enough for anyone.
As the network in question is strictly closed I don't anticipate any problems with this as the addresses would be unambiguous within our environment. I'm curious if anyone else is doing this.
No. Nobody else is doing this. You should never make use of address space that has not been assigned to you (either through a regional authority or an RFC) for use, regardless of how closed you think your network is.
I'd be very interested in corresponding off-list with anyone who's in a similar position.
I think you need to post a new request asking for help on how to efficiently allocate RFC 1918 space.
From your website it looks like you're a consultant... If you're acting as a consultant for someone please do not violate the RFCs, they exist for a reason. Ultimately you're creating a nightmare for the person who comes next and is tasked to clean your mess.