I saw that you may already have this in your head, but I will confirm it for you. From everything you are describing as your wants and requirements, I really see only one direction for you:
JC-120 is the first thought that popped into my head!
JC-120 is definitely a workable amp for Weir stuff. Used to use one myself.Believe it or not you can get Jer tones out of it too. It is just a strong CLEAN amp that acts as a great pedal platform.
I think he could also go outside the box here and do something no one else has done. To my ears, the chime Weir got from 75-82 (and yes I know you can find distinctions within that period, but lets keep it simple) has an almost "direct" like quality to it. I find myself sometimes just totally falling ass backwards into a situation and then saying "wow that sounds like 78 Weir" .
The last time that happened was just 2 nights ago at a Shakedown gig. It was the end of the night, closing song and my Deluxe Reverb went kaput (blew or shorted power tube I think,I havent looked at it yet, but I got it back once by flipping the standby switch quickly like 6 times and used it for about 5 more minutes before it went ) anyway, for the last song I plugged into the keyboard players Powered Personal monitor a mackie SRM 150 :
It is like a hotspot. It is just a self contained powered speaker. I swear to god it had the Weir chime! It had a little bit of help as we jumpered it to a 12 inch powered mackie speaker. It sounded remarkably good and cut right through the mix!
Michael, you and I have known each other for quite a while now. I have watched a ton of gear pass though your hands
Start checking out some direct sounds via solid state equipment, and then build back from there.
Im actually going to do that myself.
The best way I can describe the key to Weirs sound from the era that both you and I love, is that it sounds "direct" even when its not direct.
.......................................................have you heard the one about the yellow dog?