You mentioned a "short tutorial for noobs" so I assumed that you were not just refering to veterans.
As for testing the weapons, thats kind of a touchy situation. It's a good idea on the surface but I don't think it's as practical as you would assume. Where would they test them? These things are pretty powerful (destructive) and presumably loud. They would need a large and secluded area to do the kinds of tests you describe and there is a good chance that they would be discovered during any testing sessions. That could be a violation of Gantz rules and could result in your head blowing up.
Personally I know that when (not if, WHEN lol) I survived my first mission and found out that there would be more, I would be thinking of ways to get an edge. I'd wear my suit under my clothes 24/7. I'd take one of the guns and play around with it somewhere. probably also check out that room thoroughly at a time when there isn't a mission as well. And I would grab all the cool stuff before the noobs realized what was going on. Remember Kurono before the shorty alien mission, grabbing like 4 guns? Thats me on EVERY mission after that 1st one. 2 Guns, 2 rifles, captur gun, cloaking device, monocycle and a sword.
I only see two holsters. Unless you have a third hand, no way you can carry more than 4 weapons (exclude monocycle and cloaking device).
It's funny that given all of Gantz' technology a strap for the X-rifle is too much to ask for.
Too bad the Osakans can't wear the BFG on their backs like a backpack.
A strap for the rifle? Why not just bring one with you? You can bring objects to the Gantz room.
Not, I agree that the "new" Gantz people would be quite difficult to train. But after their first mission, I'm sure they'll be willing.
About training. Remember how Kurono trained the team to jump around the buildings (skyscrapers)? They should be doing that kind of thing a lot more. I'm sure they could find some woodsy remote place and experiment with the guns.
To be honest, If I went through this kind of thing, I'd be pretty freaked out on my first mission. But after that mission (if i survived), and when I realize that my life is in danger and I have to defend it, I would train like hell in my off-time. As in the time when I wasn't going to the room. Screw going to school, this is my LIFE in danger.
Ok for starter i would like to say i love the gantz manga for several reasons. it is a great manga because it is different from the rest of the other manga in that it focus alot on personality of different people in different situations. It also portrait some realism in the manga as in not everyone is a heroe, not everyone can be sefless and fearless. I mean come on if i think i was dead then get resurected and then have to fight Giant aliens, shit i would piss my self if i walk down a street and see a Lion or a tiger already let alone a t-rex, so yah different people will act differently in certain cituation. Oh and on the not of fully using all the weapons gantz provided. well first of all you just die and you've been given weapon with technology that you never even dream of. how the hell can anyone use it effectively. speaking as a normal person. now if you are a train millitary guy, like that sniper in the temple mission where he actualy tested the gun and snipe aliens from afar. so once again that is different people act differently in certain cituation. I also love this manga because some of the character personality in this manga is more believable. example Izumi, he is proud because he already beat this (game) once or maybe many times before. and that he also think all the noobz are useless which is why he goes off on his own, when you can't trush anyone then you can only trush yourself. which at his moment of death he realize that sometime being alone will get you surounded and no one's there to help you. As for Kurono in the begining he likes to be a heroe do crazy stuff, just to prove that he is better than kaito. which he is in my opinion. then once he meet Tae he change, to a more rounded person. That is why the gantz team from then on are doing great, more teamwork, they even practice to use the weapons gantz provided. I mean if Kurono didn't leave i bet the tokyo team, under his leadership would be better than the osaka team.