1) For the convenience of modification, it is better to have a built-in option than a script.
2) I just need different, types of soldiers to have restrictions on the use of certain types of weapons. For example, Snipers cannot use rocket launchers.
5) For cargo ships, so that they can transport UFO components, ship weapons and armor. Everything that the landing ship does not need to transport.
6) I know, but ... it's just a dream.
1/ Use scripts. Ruleset is convenient for you, but it is inconvenient for us. Once script support is added for something, adding hardcoded ruleset attributes is harder to do, harder to maintain and can break existing scripts.
2/ I know it from other games, e.g. Xcom2012, but I think it is total bullshit.
I can hold a sniper rifle,
my grandmother can hold a sniper rifle,
Britney Spears can also hold a sniper rifle.
I am not going to implement limits on who can hold what.
What if I just killed an enemy who had a sniper rifle and want to steal it and abort the mission... I cannot?
I can imagine modding accuracy on specialized weapons for untrained people... so that Britney Spears has only 5% accuracy with a sniper rifle, but I'm not going to disallow her using it.
5/ Same argument. If an item fits into the ship's cargo space, I'm not going to disallow loading it.
Also, why are we even talking about this? If you need to transfer something from one base to another, just send it via Transfers... cargo ships in Xcom are useless and I don't see any reason to implement them.
6/ No.