there are many good points to be made as far as FTG technique being a Bloodline limit,Please read carefully. I said "If it's not blood line limit, then surely all the jounin would be capable of doing it to some degree." My "to some degree" is similar to your "talent and skill" concept I think.
So far we know 5 people that can do Rasengan not 4. You missed Konohamaru. Now Rasengan is an A-rank jutsu, it's a shape manipulation techniques, but the reason not a lot of people can do it is mainly because it's not taught widely. It's very hard to master, because before Naruto, you have to have excellent chakra control to master it. Naruto use a clone to do Rasengan, that way you don't need excellent chakra control, hence Naruto and Konohamaru are able to do it.
Sage mode is even more picky than Rasengan, you need a teacher with you all the time at first and then you have to learn it in mount frog (at least if you want to learn it fast). Even then if you are too successful, you turn into a stone frog. The fact is sage mode is not blood line limit, everyone could learn it, you don't need certain blood line to do it. The frog stones in mount frog are the prove.
Just because some jutsu only mastered by few people doesn't make it a blood line limit jutsu. Blood line limit jutsu is a jutsu that can only be performed by someone with specific blood line. Now the manga told us that the 2nd, 4th and Tobi all has space/time jutsu. If the space/time jutsu is not blood line limit, please think the points below:
1. Logically the 4th learnt it from Jiraiya.
2. Surely Kakashi the copy ninja would be able to do it.
3. It won't hurt Konoha to have a lot of shinobis with space/time jutsu.
4. Surely all the Konoha's badasses should be able to do it, the sannins, the 3rd, Danzo, Itachi, etc.
5. With enough people (say 5 at the same time) mastered the space/time jutsu then Konoha would be unbeatable. Look what a trouble Tobi is. Look what Minato capable of, sending the 9 tails attack elsewhere.
You could have all the creativity in the world, you may have all the talents in the world, you might have never gave up attitude all you like, but if it's a blood line limit jutsu and you don't have the blood line part, then you WON'T MASTERED that jutsu.
One of mine would be that the 3rd was suppose to know all the techniques in Konoha, yet no one ever mentioned the fact that he knew FTG, I think it was left up to everyone to kinda figure out for themself the techniques that the 3rd probably didnt know. Those being the ones that require a specific bloodlinelimit.
Also it would seem that Oro would have definatley tried to master that one instead of fooling with animal experiments and such