Ok, enough reading and researching over the past days.
I had a “go” from my friend for a potential switch to a Simplex rd, provided it’s a nice one with no or minimal delrin. If I understand correctly the Simplex range, this basically narrows down to the SX410-610-810 and the SLJ models.
Among the SX, the 410 seems the most available (but not the GT version).
Concerning the SLJ, among the different posts, I read verktyg impressive tests on these models and how they might not clear on some >24t fw if cogs are too close (e.g. 7s fws). Also interesting were some comments on how it could possibly be hard to wrap chain if a large triple crankset is used, and on how it is not easy to recognize Simplex models (the latter point being reassuring as I was starting to doubt about my cognitive skills when going through the Simplex catalogues )
Given my project would require a triple crank and an up to 24-28t fw, it is important to identify the proper Simplex rd model and mounting before spending money to purchase it.

Here below some SX410 photos from ads on ebay, I’ll post some SLJ asap.

Ad no. 1




Ad no.2