DaveO,
If I understand your first point about randomly accessing different versions of a mix, the answer is yes. The minidisc player operates just like a CD player. You can switch to different tracks.
Secondly, the MD player/recorder that I have has an automatic and manual level control setting. It's default position is the automatic setting, but If you want to do it manually, you can easily do so. The only thing is that you have to commit to a manual level. Once you start recording, you cannot change the level during the recording. If you're careful, distorting should not be a problem.
As for the A-D/D-A converters, they sound real good to me. For what you're going to do with it, You should have excellent results. The unit is real quiet. I have been very happy since I've gotten it. For the price, the minidisc option is a very good option if you can't afford something else.
By the way, do you have a computer? Don't forget that you can get a CDR for about the same price as the minidisc. If you had a capable computer this would probably be the best option (non-compressed format, CD players are everywhere, make demo CD's to send out, etc), but then you'd have to start thinking about a capable sound card... Mo' money.
Last thing, the Sony MD unit comes with an optical cable. So if your MD8 have an optical/digital output, you could transfer stuff into the MD digitally, even better.
Rev E