OK, spit-balling here. What if track one recorded the input then track two recorded track one, etc? You set the track as the source in the record settings for the track under SRC3. T1=Track1, etc. You can have the track play its own record buffer. You might even be able to get track one to record whatever’s coming out of track 8 in addition to what’s on the input. I would have to imagine it would be mostly noise at that point but maybe that’s what you want.
I’m having trouble figuring out how to get the phrase longer than 64 beats but I’ve never used a combination of recorders and whatever they call it when you string multiple patterns together. I’m wondering if you can get away with slowing your tempo down to the point where you don’t mind the 64 beat thing. Also don’t know what role the buffer size limitation will play. Also no experience with pickup machines other than they have an overdub mode.