Probably because of
this. 79.3% of all players polled voted for instanced content over the competitive content you are asking for.
The lack of response so far has to be 1 of 2 things.
1) They aren't going to do it, but do not want to say no flat out because of backlash they would get from the people in favor of HNMs.
2) They haven't had time to even look at it / give a definate answer yet because they are prioritizing other things first.
Honestly some of the ideas in the OP for different ways of spawning NMs seems very interesting and fun (sans the timmed HNMs but I've said my piece on that.) I just wouldn't hold my breath for a response.