Since you're taking the time to sort through these suggestions by listening to the records, maybe I'll expound on my suggestion of Steve Lacy-Mal Waldron: Journey Without End. I think it's a good candidate for a few reasons:
First and foremost it's a great record with great playing by two all-time masters (also their first record together)
It was released in Japan only on Victor and I don't believe it's ever been on CD.
Unlike many of the encounters between Steve and Mal, this is a quartet record, not a duo which I think makes the music more "marketable"
On the latter point, the leaders also have high visibility which might secure more sales.
If you ask me, this sounds like what you're looking for: a rare, unavailable on CD title with impeccable playing by two amazing musicians. It has some historical significance, and, if it came out next year it would fall in-between the ten year milestone of Waldron and Lacy's passings. I think it would make a fitting tribute and would be enjoyed by just about anyone who bought it.
Just my two cents on the matter. Others may disagree.