There is literally no difference (except for power capacity) between a lithium coin cell battery and AA lithium batteries you can just install in your CPU battery pack. If this is what you are wanting, don't bother converting to NVRAM.

What you are asking is not possible as the RTC resides on the ASIC.

AA Lithium batteies should last 5-10 years depending on the climate the machine is in.

If you go with lithium batteries, there is no reason to even bother with a remote holder; in the extremely rare event these do leak, you will never see the kind of corrosion you get with alkaline batteries.

again, replacing alkaline batteries with lithium batteries is zero effort.

I guess...just didn't occur to me as no one but myself has ever worked on any of my machines.

Perhaps when I'm no longer part of this world.

At that point everything will probably go together including all my PCB repair gear, spare boards, spare parts, etc...