I think you are very much on the right track, MoT. You know your child best.
FWIW, my opinion (not a dictate!) is that long-term goals for handwriting should be the ability to 1) sign one's name, 2) fill out a form, and 3) write a thank-you note. Anything beyond that would be gravy.
On the question of the learning & memory benefits of handwritten notes--not from the research, but my conceptualization: well, presumably some aspect of the value lies in multimodal input and rehearsal of the content of the notes--which relies on those notes being encoded as language. In the case of persons without handwriting automaticity, one may think of letter formation as processed more in the form of a small drawing task than as symbols representing the components of language. This suggests that there may be some L&M benefit from handwritten notes, but also that quite a bit of the brain that one might expect a NT student to devote to processing language and concepts is instead diverted to other, mechanical, purposes. Also, lengthier content may be processed incompletely or spottily, as some may fall through the gaps of divided attention. The bottom line is, if one has to think about the act of handwriting while taking notes, one has less attention, memory, and reasoning to apply to thinking about the content.
As to how she might reintegrate into institutional school...that depends a bit on the timeline. By the time she reaches middle school (and certainly high school), it is highly likely that there will be some option for, at a minimum, BYOD (bring your own device). Most of the suburban districts in my area are moving toward universal 1:1 tablets or netbooks beginning in middle school, and nearly every high school already at least allows devices. The secondary school where I work has provided 1:1 chromebooks for several years (the first cohort with devices all four years graduated a couple of years ago). And finally, most districts have also moved to online state standardized testing. (Our homeschooled dyslexic/dysgraphic DC integrated quite well into a public secondary school with no accommodation plan, due to the presence of universal 1:1 chromebooks. I think the bigger challenge was getting used to the idea of changing out of one's pajamas to go to school!)
IOW, at least in NA, the unaccommodated, general education classroom is moving rapidly toward negligible handwriting demands anyway. This, of course, is why your child OT thinks handwriting is anachronistic. Because educationally, it is. I will note that there is value in learning to read cursive, as otherwise, a fair amount of historical text becomes inaccessible--such as grandma's letters or journals.
