Mark is not interested in working on live recording but allow to release them.
For the Alchemy DVD/BR I don't know if Mark was in position to veto it as he had already given his approval on the final work at the time of the video tape release and thus don't own the commercial control on it anymore.
I think Alchemy was a bone throwed to the fans: without it, there would be no version of Sultans, TOL and TR on video ! I can imagine that Mark ok'ed it because:
- It costed nothing, it was one of the very rare recordings the band did by themselves, so no fight for the rights (for Wembley'85 it would have required to go and discuss with Channel 4). It was ready out of the box, and Chuck Ainlay who recovered the tapes was enthousiastic about both quality of performance and quality of sound.
- Mark's clothing on Alchemy (red jacket and shoes) is a little less ridiculous than the cow-boy shirt of Live Aid, the sleevless blue T-shirt of Wembley, and the clown costume of Sydney'86
- Alchemy sound, being more sober than BIA tour recordings (no overdriven-to-death drums, less overdrive in the guitar, less "80s" sounding synth) fits better with what Mark is doing today (very clean sound, no artefacts) and hence he was not hostile to releasing it.
- And of course, it was a legendary concert with probably the best possible sales perspectives. Not sure if this was a commercial success though.
Alchemy is great, but this was 30 years ago. Alchemy II is more than needed...