As I've said previously, you're talking to the wrong end of the ATC animal. Your management needs to talk to our management for change to be implemented. We work within a system so, as such, work the way the system is designed to work. I have to work within the confines of the system as it exists. Provide me with a system that works the way you want it and I'll do it.
I'm sorry but as a line controller I sometimes don't have time to worry about the niceties. Maybe I'm too damn busy to consider you earlier than I absolutely have to so you get your 10 minute delay when you call me. Other times I'll have enough time to look out a bit and tell the sector that has you there's roughly a 10 minute delay so speed reduction approved. Assuming I can get a word in. Maybe they're really busy and here I am trying to bother them with non safety-critical information.
You have one aircraft to manage. I have 20 or however many so my attention is spread accordingly thinly.
I fully understand it's more efficient to manage a delay over a longer period and that more can be achieved the more warning you have but sometimes I just don't have the time to do anything about it.
I'll give you unrestricted climb to your desired level at the speed you want via your preferred routing when I can. When I can't you'll be held down, slowed down and vectored. Same goes for the delays. Sometimes you'll get it the way you want and other times you won't.