I agree with you, but have a few comments.
You cannot really use AR15 type grips… Seems kinda dumb to not make them 100% the same. KAC is probably better here…
You cannot even get barrels, so the quick change out is largely wasted.
Although the scar has great railspace when compared to the HK 91, when compared to the M-110 it still sucks.
Getting extra parts can be pretty fun, if possible at all. What happens when you need another barrel because yours is shot out? You call FN and they tell you to go fuck yourself. Any HK91 that needs a barrel can easily be done, any FAL that needs a barrel can be done… God help you if you need extra parts and you can not just wait for them from FN… I would hate to be in some 3rd world shithole and need something… Even something as dumb and mundane as magazines.
Mag prices. G3 mags are like 1$ each and everywhere… SCAR 17 mags might as well be made in gold. You do not usually see HK mags that are cheaper. 
The Scar-17 is great. I would love to have one, but I never like to see people needlessly bash good tried and true weapons like the FAL, the HK91, and the AK. KAC makes a really good product also, and honestly they support their products much better. The scar is awesome, but I do not think it is good enough to lash out like you did… Here are my issues:
1. How hard would it be for these jokers to make a plastic lower that takes mags that are not proprietary? SR25 mags maybe?
2. How hard would it be to import a boatload of barrel blanks (or just like, buy them here from a good source) and profile them?
3. Magazine availability! How hard is this??? You make a special mag, so make tons of them and make them cheaply. Contract Magpul to make mags for god’s sake!
4. Put a good trigger in it! 3000$ rifles should have good triggers!
5. Sights, having barrel-mounted sights, with a removable barrel seems kinda counter-productive. Many people dislike gas blocks with folding sights. The LMT MWS seems to be much cheaper if you actually intend to own more than one barrel… In many ways it is a good solution to the same question.
6. HK91 can be a host to a legal Autosear, the Scar will never be.
7. HK91 clones with quick change barrels exist…http://www.youtube.com/watch?v=phG9x2hsj5Q
To me it just feels like you are some 20 year old MMA winning cage fighter that is beating up on some old guy from 1940.