Volume control and/or pause button

I agree, that there can be a huge difference in volume, like on Youtube, Vine or Twitch too.
But I would rather stick to adjusting the volume yourself and additionally reporting those loops that are true earrape, than getting your hopes to high, that the platform will solve this for you.
Even the VLC media players doesn't get automated volume correction that right.

Try to remember when you had to increase the volume for a more silent loop, and decrease it before going to the next one.

There is nothing that the webmaster just can apply to an .swf to unify it's volume to a certain level.
He gets the compiled extraction of the loop and wouldn't have the time to edit every single loop anyway.

That's probably Eins right now: