I'm not quite sure I know what you mean by destructive editing - removing/rearranging an audio loop, but see below anyway.as I said - I'd like to hear about a workaround with the non-destructive editing...?
The easiest way to get around the above situation is to create the midi clip in live, and send to your external gear, then record your gear into live. This way you can trigger your midi loop to start and record the incoming wave all at once on beat.this is a bit painful if you're planning to record hardware synths and especially if you're going to edit a recorded audio-track and match it to the timegrid/transportbar/whateveritiscalledinlive... it's pretty hard if as you can not see what you're doing as you're in the seperate wave-editor.
Back to the editing -
There is not a separate editor like cubase has, but when in the arrangement view if you modify and audio clip you can then turn that into it's own separate clip.
ie - you have a 16 bar loop that plays for the first third of your song, but then you want to change it to a 4 bar clip with an off set start point to create a new rhythm. The new 4 bar clip can be created with in the arrangement view for you to use.
As well since you can use envelopes on the clips for volume and other clip properties you can do other "edits" of your existing clips.
When it comes down to it, I think you can perform most audio edits you want in Ableton, but it's not as intuitive as an external editor is.
If you want to be more specific about what audio editing you want to do then I can tell you if it is possible or not.