Given your thoughts on Spaces you may well be interested in the new check box in the Spaces preference pane in 10.5.3 as it will get things a lot closer to the way you want them.

It's not perfect as it won't let me have different behaviour for apps tied to a single space vs. those which aren't, and although clicking on an app's dock icon will cycle you through the spaces occupied by that app I can't find a keyboard equivalent.

Still it's getting better.