When it comes to the Achilles Heel aka the DIS module, we all share your concern; the ECM - not so much as they are available, and just in the past week(s) Marc Haibeck is starting to referbish the ECMs.
Jerry's Gaskets is progressing toward completion of that DIS module, and we all are on the edge of our seats, far as monitoring progress. But, then again, MegaSquirt has developed an ignition system that piggy-backs on the stock GM system (as I understand it).
Note: Fortunately, the DIS module is very robust and NOT a common mode failure item. However, HEAT is always an issue, far as electronics longivity is concerned. One of the advantages of removing the coolant circulating through the TB is the considerable reduction of heat transferred to that DIS module - at least while the motor is running.
I'm reminded of a Ford Model "T" car club I read about. I came across it while reading a post on the CF FORUM (IIRC) which was dealing with this very subject. The OP was concerned about parts for his early C4 and expressing some panic (if that is the right word) over locating parts. The responder with the model T assured him that through his club and the ability of many to fabricate parts otherwise unavailable, that the concern was largely mitigated.
And SO, I believe, it is the case with our cars as well. Far as I know, there aren't many - IF ANY - cars that are parked for lack of parts OR a reasonable solution to work around. And, thank Lotus and Mercury Marine for building such a robust "bullet-proof"
motor that doesn't fail often.