Just to be clear it is not something I need/want to do (I've got msc400 and MRX1/2) -- just a point for discussion.

I think that base station could be a MRX1/2 with RFX250 or other RF device. The Remote would not need to be network enabled just communicate with a network device (with firmware mods to support). You're right it will not happen but missing piece seems most likely to be that RF protocol and does not support encapsulating message so MRX1 could de-encapsulate and route as required.

Again, it is just a thought not to disagree or start a debate.