I don’t think that would really work. It’d be much easier to just leave it as it is and if someone needs to come inside for cover, just open your door for them. As for looting, my loot is always behind multiple doors and protections. If I let someone in for cover, they’re only getting in the first level of security. Anything more than that and I run the risk of them turning on me and stealing my stuff.
I personally like the door system the way it it to be honest. As for a party system, if this is launched through steam there would be one in place through that.
There is no point in over complicating this to make it “easier” or in my opinion dumbing it down. I don’t want a game just like the others. I want to have to worry about shooting someone running up to my house in case they’re a friend, its more realistic.
I do hope however that they eventually add more customization options into the clothing/armor. It’d be great to be able to have your entire clan in blue or red or whatever and equally awesome to be able to put on an enemies colors and infiltrate their base for a raid.