As far as scopes not working in indoor games, I beg to differ. You can't use a scope at an instant, but you can make short work of people on the field that are cowering behind something and peak out only for a second. Due to the lack of instant action that a scope has, you're also limited to watching your shots, or even being supporting fire only.
My personal use of a scope in an indoor area worked out quite well. There are some longer stretches that a scope really comes in handy, and can give you the upper hand at times. If you know someone is peaking out every so often just pumping off shots to get your team to keep their heads down, you can just kind of watch the doorway through the scope, and that's the end of that.
Realistically, though, an RDS would be superior for fast-action situations. A scope in fast-action can get in the way since even your iron-sights are hindered.
Primary: Custom WE M16A3
Secondary: KWA MP9
Side: Custom WE M1911A1