New plug developers are always welcome, but I'm not so sure a new sound plug is warranted.
Granted its use is less than straight forward, but it has most of the functionality you described.
Not sure exactly what you mean by 3d sound, but the positioned sounds should enable you to replicate that.
Now if you were to do a full blown sound system, something that did synthesis, as well as playback...
That would be well received I'm sure.
Also on the RTS, to me that's more of a documentation issue rather than bad planning, as it can be avoided by simply using a different expression.
There is a point where you have to choose between functionality, and ease of use. That falls in a gray area... somewhat.
Anyway, welcome to the board, and happy Constructing.