About your first idea (sorry don't know how to do the quote thing) I don't think the workshop skins would really work out but I do know on other servers how their !ws command works is you can choose any skin from any gun. For example say your favorite skin is a P250 white out, you will be able to choose the gun you want the skin on, what gun that skin is normal for, then once you select it it will equip. The only problem with this !ws plugin is the skins don't really change to accommodate the gun so if you choose a really detailed design skin that's normally for pistols and try to equip it on an AK it will be stretched and doesn't look as good.
For your second idea, I would love to see more player models!
And for your last idea I do not support that, I would hate to see SG jb turn into pay to win