WowAce

It would be nice to define an area in which grid will automatically layout itself into.

So for example if I define an area of 500x400 a
- 10 people raid will generate buttons sized 100x200 (5x2)
- 25 people raid will generate buttons sized 100x80 (5x5)
- 40 people raid will generate buttons sized 100x50 (5x8)

This should make it easier to layout your interface around grid so it always covers roughly the same area.
There should be two additional options for that:

[on/off] Size to fit width [size]
[on/off] Size to fit height [size]

The width and height settings should be reflected by the size of the background.

That's not really possible with the Blizzard Headers.

Individual frames can be sized up front, but for layouts with pets you cannot really predict how many pets there will be.

I have switched my grid to being in center bottom so I am interested in something like this. However I do not see a way around the pet issue.

Eventually you will be able to customize the frames to the point of specifying size as well. That will let you manually size things to fit. We are not there yet though.

Just a clarification question - you can resize the grid frames during runtime using the options panel already - why is it not possible to do the resizing based on a function? I don't know much about the blizzard API here, but I've seen a lot of addons providing resize options (Pitbull for example) which work interactively - so to me it seems possible to resize a frame based on - let's say - an event callback or sth. similar?

I see that pets are a problem, but that would be only when the number of pets exceed a multiple of the number of columns (new row if numPets % colCount = 0). And that won't happen very often. So as a suggestion (again - if that is possible) - introduce a counter that resets to 1 everytime you enter a raid. The numbers of rows equals raidsize / colCount + counter (3 for a 10 player raid with 5 columns per row). If the number of pets increases beyound a multiple of colCount an additonal line is added (the counter is incremented by 1). If you don't decrease the counter the frame size will just switch once but stay stable for the rest of the raid which would stop the frame size from switching back and forth all the time.