would something as simple "vertical leg-hip raise" (as named in the directory) be good enough
to give the RA a good workout? or do i have to resort to weights? i REALLY don't want to put
any un-needed tension on my lower back.
Weigths are not necessary, if the exercise is challenging enough. It just gives you different amount of stress. But, as long as the exercise is challenging (When you can do less than 30 reps in a rows, it's my opinion of challenging). Leg raises do stress the lower back, but not too tremendously. They also work lots on the hip flexors, so try to focus to using your abs.
the Obliques are a-bit harder for me to choose from the variety of ex's there are... maybe
im not fully getting this but if the "Auxiliary" ex's are "extra" does that mean that those
aren't enough on their own in order to strengthen the muscle? if so than things like
the "Lying Twist" (which seems awesome for me to start from) is not usefull and i have
to resort to things like twisted crunches (which im not a big fan of)
Okay, I'm not following you here. What do you mean by Auxiliary exercises?
I wouldn't personally do either lying twists nor twisted crunches. But if you want to try it out, you'll find out very quickly if that exercise hits the rigth places. Don't go too deep into exercise descriptions, just try things out. Obliques rotate, prevent rotation, and take part on lateral flexion and general stabilization. You'll find the best exercises for yourself.
we do have a machine kinda like the lever seated side crunch but machines always rubbed me the wrong way.. as if im missing something...
Personally, I think you can get a bang for your buck without machines as well. Cables are alrigth.