I like the direction the section variables are going. I've been using them extensively the last few days and a few things came to my mind that could be added as additional features. Mainly these are things you need for positioning items:
The "Right" and "Bottom" settings would be the equivalent of the "R" you can use in relative positioning without the section variables. Constantly typing [Meter:X]+[Meter:W] gets annoying after a while. The center ones come in handy when you want to center a meter on another one. Not absolutely necessary though.
We have not talked it all the way through in the team, but our initial reaction is not to do this.
The main reason is that it is just "shortcuts" for existing capabilities (i.e. [Meter:X]+[Meter:W]) and would require a lot of added functionality to really work in a correct and complete way. The values of X and Y are altered by StringAlign as well, so we need to fully flesh this out with Top/Left/Right/Bottom in order to ensure we have all the bases covered with Center, and to be honest we think it is more flexible and just as easy to have the skin author "cook their own" formulas using existing values as it is to try and have Rainmeter account for all possible scenarios.