I usually use a mix of :
- "Say requested level" : because I don't trust much the figures your ops filed. Only you know the level you wish.
- "Are you able FLxxx ?" : only when I think changing level would be an easier/faster solution to solve a conflict than a strong vector.
- "Due to converging traffic, do you prefer FLyy or a right/left turn xx deg for XX minutes ?" : If I've got time to sell my carpet, you've got time to think about it and tell me your price. And the solution should fit.
- And some other tricks of that sort...
One advantage I have is that I still use my voice on a VHF frequency. CPDLC will certainly kill that.
I don't know much about oceanic control (I just do what they ask me to do), but I believe ACARS and HF don't help them for human-human negociations.