When I was looking at a set of winter tyres I asked Admiral if they wanted the details of them and whether there was any issue with them being run-flats. I spoke to two people (I rang back and asked someone else, ever the skeptic) and was told both times "We don't care what tyres you run, run flat or not it makes no difference, and neither does the make. If they're legal, you're insured" - almost word for word the same reply.
Understand and agree with your reasons for changing. I've done it both ways, including uprating suspension when I took the RFTs off etc, in the end decided that I'd rather have the RFTs for peace of mind and I'll change them for non-RFT if/when I have to. They're all available in a day or two from the factories, so it shouldn't ever be an issue, but in the worst case scenario just change the affected axle and then do the other one when you get home (mixing RFT and non-RFT isn't great, but it'd do for a day or two).
All opinion-based though, as I say, your car your choice and it makes sense.
