That is a nice option to have, but obviously it does have some specialties to it, which I would like to comment on today:
In difference to all other instruments one can choose to upload on wikiloops, the mixer option does create a very different feeling and is eyed much more critically.
That's easy to understand if you know wikiloops a little:
First of all, people get notified about remixes, and expect to find someone added an instrument, which is the common case.
If someone added let's say bass, the addition may be poor, bad sounding, or really great - no matter, it is quite easy to deal with that, since there is always the feeling of: Someone added something that was missing, maybe in a not-so-great way, but the act doesn't say my track was flawed - it was just missing bass.
When the chosen option is "mixer", that always has the ring of "my track must have been flawed, otherwise no one would have felt the need to do a mixer-remix".
If the new remix is of outstanding quality and exceeds my own mixes sound by lightyears, I'd be happy that someone with some skill took the time to let it shine - if it sounds quite similar to what I produced, I'll feel like "What is she/he trying to tell me by doing that?".
It's quite simple psychology there, so I would strongly advise anyone to add some words of explanation to any future Mixer uploads:
What did you do / change/ EQ / comp, and what made you want to try that - that would be the best way to avoid the kind of misunderstanding.
Thanks for your attention :)