My view is that the Avionic set up in GBEBZ has some very clear thinking behind it and has the maximum system redundancy for the least cost.
Awwww shucks... That means a lot thanks
To be honest, I also have iPad, Skydemon (who doesnt!) and a iPhone in the plane should the worse day happen to me.
The reason I had to add another DME box is that the old KNS80RNAV box used to have the DME as part of that, so when removing that I needed to install a new DME or lose that facility - DME is still very much used in aviation (even bigger planes use it).
Even "shooting approaches for fun" requires reliable trustworthy kit
I take your point about the long term support - but think that might be someone else's problem in 10 years