I don't know about you, but I wouldn't want to spend thousands of dollars on equipment that has been repeatedly rejected by the Army for not meeting minimum standards, and weighs significantly more than what is standard issue.
Dragon skin is fine armor so long as you don't expose it to extreme temperature (like say Iraq or Alaska) or diesel fuel (like from a HMMWV or Bradley fighting vehicle) which can cause the glue to fail.
Heckler and Koch make some fine firearms (hence the price tag) but unfortunately none of them meet the requirements of the Army's missions. The 416 was a nice concept and has caught on with the civilian market, but was hardly improvement enough in reliability to replace our entire inventory of rifles (especially when factor in the greater expense of the new rifle, the cost of retraining your force to maintain it). To top it off, the 416 with 10" barrel weights a pound and a half more than the M-4 with a 14.5". That's weight gain and range and velocity loss. Considering that of late we've been issuing of M-14s and accessorized M-16s (bipods and ACOGs, oh my) because current operations require engagement at longer ranges, the M-16A4 is my weapon of choice.
I've seen reports of highly modified MP5s that might reach 200 meters, but as they say, rifles are rifles and pistols are pistols (guess what the P stands for).
The pistol used by the infantry is the M-9. You'll probably never use it (in an infantry company of 100+, we had 2 pistols that went to the CO and 1SG)
I think in the 10 years I've been in the Army (6 infantry) I've held maybe 5 grenades. They were all standard issue frags and highly accountable.
For accessories I managed to get away with a 4X scope, but units will have varying policies. Also those that constantly qualify at the expert level, wear an EIB, and sport sergeant stripes can get away with some things that marksman scoring privates can't. All that stuff makes little difference anyway. Learn to use your rifle first. Spend about 50,000 rounds before deciding on an upgrade.
Advise for basic: 99% of what you have heard or preconceived about the Army is wrong. Go there with the attitude that you know nothing.
This is a ten level task