For me, this is one of the biggest issues I run into all the time in both Go and Pro design. I'd suggest XCode and/or html's handling of object resiing (tables, divs, etc) in web space would be a second obvious one. These both provide 2 things we lack right now in FileMaker:
1. The ability to have groups of objects proportionally resize together.
2. The ability to choose between percentage-based or manual sizing.
Right now, we often have to resort to tricks like using horizontally repeating proxy fields that can resize together (with limitations). More often, particularly in lists and portals, we simply accept having a portal with a single row that endlessly resizes, which means that our portals lose elegance and meaning at larger display sizes.
Now that FileMaker has a DOM, it would seem more doable to implement something like this than it has been in the past. Something as simple as Vince's idea of letting us check objects in a group that should expand together instead of individually. If we add to this the ability to nest groups and assume we could nest these settings, we'd have a highly flexible approach that would open up all kinds of icher, more flexible options to us.
Something I've suggested before in other forums would be to allow us to resize objects together by giving us the ability to anchor objects to other objects, which could implement most of the desired behavior.