That is unless you are looking at the lenses you mentioned earlier 17-40/16-35. Even so, I would rather suggest you look for 2nd hand 17-55 instead, since 17-55 comes with IS while both 17-40 and 16-35 doesn't.
And in regards to 70-200, there is no right or wrong to whether you want to use that lens on crop or on FF. It's only the matter of need. *I quite like the 70-200 on crop, since it gives me a lot of reach as compared to FF.* And you also said that you are not comfortable to carry heavy gears ATM, fyi, 70-200 f2.8 weighs ~1.4kg (and the IS II version costs ~3k, non-IS cheaper abit)...
If you are trying to think thru the upgrade/new acquisitions of lens...
- Identify what you want (more reach? macro? or large aperture?) *be truthful to yourself. If you have no clue, DON'T BUY ANYTHING!*
- If looking at image quality upgrade, what are the FL you usually use. E.g. If you want to replace your 18-55 for better IQ, but most of the time when you shoot, 20-50mm is enough, then a upgrade may be 17-55 or even 15-85.
Considering that you are going to FF, When are you moving there? 1 yrs, 2 yrs time? During this period of time, perhaps you could have got a 2nd hand lens and enjoyed using it for this period of time and sell it off at little loss when you eventually move to FF.
That said (as also like I mentioned earlier), you are always free to buy anything even if the world is against it.. Since it's your money and your choice.