I want to give my opinions on this, as I like some of these points a lot.
E++ Should get private servers for games like murder and creative.
Honestly, PZ isn't too big, so it's easy to make parties and invite players into games that way, so this idea won't really work. Once PZ gets bigger, then this would be a great feature to add.
E++ Should have a better name, Eg: Platinum, Premium, High-Class, etc. then add Premium+ or smth.
I honestly agree with this. E++ isn't too interesting of a name. Of course, I don't want another rank after E++, but having a plus in the name would be great so these players can also change the colour of the plus like E+ can. The name "Pariter" doesn't seem too interesting (sorry Jules), but I do like something along the lines of DJ+ or Raver+.
E++ Should get chat colours.
This could become very annoying for other players. You would already have access to coloured signs, so I don't see a massive purpose of having chat colours. Also, colours are often used by staff to announce something important or host an event, so this would cause a lot of problems for them. However, I think allowing E++ to have italic, underline, and strikethrough in chat would be fine in my opinion and would give you more options to talk to others. So leaving it at italic, underline and strikethrough is enough.
E++ Should get more plots, ofc. Maybe bigger plots too?
Of course, they would get more plots. Bigger plots, maybe not since you already have access to plot merging.
E++ should have customizable rank colours, or maybe name colours.
Elite+ already have access to change the colour of their tag, so of course, E++ will be able to do that as well. Name colours could be a good idea, as long as we limit it to colours that won't hurt people's eyes.
Great ideas

Like Jules said staff can comment on these things. It's usually the forums suggestion team that work for the QA team that sort these suggestions, so there isn't a big worry on staff denying your opinions. Of course, why would we?