i've jammed with my guitar, pedals, looper and tempest, but just with a 808 kit i made.
if you treat T as an on the fly drum machine, it's very immediate and open to improvisation. there are so many things you could do. it's even more manageable if you stick to 1 bar and do live mutes etc. i could see maybe jamming with 4 bars and doing some synth lines also, but you'd need a somewhat involved setup to do this and it sounds like you don't want that. tempest will teach you a lot, but it takes a year or so to really get it. you need a mixer and a couple effects to make the tempest more palatable for standalone use.
if you don't want to wait for mpc live, go for an electribe 2 sampler. they imitated the design scheme of the tempest, but you can load samples into it also.