Summary: not lookin' promising.
I've had contact with some good people: a senior fellow engineer at a major ICD mfr, a former employee (engineer) of a major ICD mfr and friend of many years, my wife's niece who is a former cardiac nurse of 30+ years experience, and helpful others.
Findings:
There are reported cases of weldors returning to work with ICD's but the reports are sketchy on details. One report mentions a minimum distance of 24" between weldor and cables, work and torch. That ain't how I weld: my face is right in there with 2 diopter lenses in my mask.
The experience of having a defib misfire has been variously described as being hit by lightning and being kicked in the chest by a mule. I'd rather skip that experience. Welding is fun, being kicked in the chest by a mule very probably isn't.
I can't seem to get data on acceptable field strengths (E-field and H or B field) that won't cause an ICD to malfunction. I opined that this is probably because the goddamned lawyers make this data highly proprietary. That was confirmed by the engineer (and friend) formerly employed by a major mfr. Goddamned lawyers.
So I'm about SOL here, not being up for a mule kick in chest while experimenting, candyass that I am.
Helluvit is that I have no friends who can do TIG and MIG, though Karl Townsend's son "the kid" may be a savior. Neither of my sons are at all interested. One daughter is, and she's done some nice work with MIG but she lives in Brooklyn NY so she's not exactly local.
Mar, bless her hawrt, has volunteered that she might do a Vo-Tech course in TIG and MIG. She'd be a natural, that based on her precision quilting and prowess with handgun, both hand-eyes coordination activites. TBD how that goes, but whatta teammate for even considering it, eh? Hey, she severely aced ground school for pilot licence for previous hub in the bad old days. Highest score they'd ever seen if I recall correctly. What a fool he was for doing her wrong, what good luck for me and eventually us. Goin' on 30 years now and it just keeps getting better.
Most folks are quite happily "weld free" in their dotages, right? Still, it's a bit of a lump to be prohibited from practicing a skill and activity I've enjoyed developing over decades and frequently find useful in my shop. Oh shit oh dear, poor me.
I intend to wallow in this for a while, f*ck you if you can't take a joke. I'm not happy about this, but it's no secret that gettin' old ain't for sissies.