Just bought a turntable after doing without one for some time, and I've been slowly listening my way through my collection. Apologies if I'm arriving too late at this particular party! Here are a few suggestions, bearing in mind the high bar set by the Bill Dixon and Hemphill discs (I don't know the Steig).
Tony Oxley: Ichnos (RCA), with Kenny Wheeler, Paul Rutherford, Evan Parker, Derek Bailey and Barry Guy. Two sextet pieces, two quartets, and a remarkable solo piece. This is the third of his early albums (the other two, The Baptised Traveller and 4 Compositions were both on Columbia and were reissued on CD, albeit briefly, some time ago). As a sequence, they are a key document in British jazz/improv of the late 60's and early 70's. Oxley uses more structured compositional frameworks than was usual in British free jazz at the time, and in retrospect it seems logical that he would later collaborate with Dixon. Parker in particular burns. OK, The Baptised Traveller is probably the stone classic of the three, but Ichnos is very good indeed.
Arthur Blythe: Bush Baby (Bruynincx says Adelphi, but I have a UK LP reissue on a label called Echojazz), with Bob Stewart and Ahkmed Abdullah on congas: His early stuff doesn't seem to have been issued much on CD, and this is one of my favourites. Fierce playing from Blythe and much more varied than the stripped-down instrumentation would suggest. Some of the Columbias, particularly the ones with the tuba/cello/guitar band (eg Elaboration or Light Blue, the Monk album)are also outstanding. In fact the early Columbias would make a great Mosaic project, but that's for another thread...
Mike Gibbs/Gary Burton: In the Public Interest (Polydor). Recorded in NYC with an American band; Burton, Steve Swallow and Michael Brecker are all on song. Arguably Mike's best album, and the title track in particular is for me one of the great modern jazz big band performances. Seven Songs, the other Gibbs/Burton collaboration with the NDR orchestra has also never been issued on CD, but it's ECM and I understand that this may be problematic.