Why not just get phatmatic pro? I have it and it's great, like having a sleek, compact recycle app (& more) all in a plugin that you can run in Live.
I think it's more powerful than just being able to load a rex file in Live. It has auto slice w/sensitiviy setting and built in envelopes and effects (per slice!). I believe it outputs midi grooves too (?), however I haven't used that feature myself yet. Guru (which I also have) is another that does auto slicing really well. I think either of these plugins are great choices that complement Live with that kind of flexibility, well worth the money. Plus you can stay working in Live (simultaneously checking the groove against your other tracks) and not have to switch back & forth to another application. Unless you use prefabbed loops that only come in rex format, I think if you tried one of those two plugs you would quickly forget about rex and then you don't need recycle either.
Of course plugins cost money, but even if Live supported rex files Live would simply play them back in a clip or on the arrange window. You still need to buy a separate application if you want to actually make the rex files in the first place.
Another idea....In addition to chopping pieces out of a file & loading into impulse, you can also chop the pieces manually, turn off warping, and space them out on the arrange view. Now when you change the tempo, the hits aren't time stretch degraded. Takes more time but it's another technique without needing a plugin.