Hi folks, just a couple of ideas:
K1, have you seen Olav's tutorials? Logic 406: Olav's Electronica Workflow Tips has some great ideas to speedily and creatively arrange house music.
Olav teaches you how to pack and unpack folders, which basicly allow you to arrange an entire track within a few minutes. So you could pack a folder with your regions for drums, bass and synths, loop it out for 6 minutes, then unpack the folders and delete the regions you don't need until you have your arrangement.
Kind of 'subtractive' arrangement. Its easy and fast.
If you were totally keen on creating the arrangement on the fly, you could build an environment that allowed you to mute tracks using your keyboard. For example, C3 mutes track 1, D3 mutes track 2 etc.
Then (same as before) loop your regions out for 6 minutes, play the track, and record the output onto new tracks, using the keyboard to control which source tracks are playing.
And idea 3: you could probably use the EXS24 sampler - I'm pretty sure it can handle 8 bar loops.
Hope some of those ideas help, and if you want to make house music I seriously recommend Olav's tutorials - essential viewing!