i can try and help from what little i know about the cube.
1)depends, and i say this based upon opinion. the ME days are spread out so the body gets a bit of a break. so you can change things up with variations that help with weak links or not. depends on you. if you are seeing progress with out variation than why do the variations. if the variations motivate you, then do them. if you are not gaining or even going backwards then try the variations.
2)sure. why not.
3)if you have them, use them but they are not needed for westside IMO. sure they can help but the lack of having them will not stop you from doing a westside or the cube.
4)yes and yes. you are doing accessory work after the ME and DE days and then have an additional RE day. you can easily do special work for weak links say on DEME days and general work for overall size on RE days.
5)its westside, just laid out a bit different. you still have all the components only spread out over a longer time frame. to me it may work better for most with increased RE work, decreased DE work, and deads and squats in the same week. my only concern is when to switch to westside to take advantage of the increased ME work. i almost wonder if you could use macrocycles of the 2. use cube for off season and westside for meet prep work.
in the end, the one that will work better is the one that you believe more in and will put more work into.