I don't know about the follback feature. Valve would have to change Steam itself as Steam was initially created as a way of automatically getting the latest updates out to everyone, from what I understand.
And yes Ant, Hammer 3.x had a
similar problem that HLFix took care of. The problem there was that when compiling w/ VM's the didn't end up of a proper coord (say u scaled somethin' and the verticies didn't align right),
HLFix stopped Hammer from 'properly' aligning them.
The problem w/ the SDK I doubt can be fixed by anyone other than Valve. I VMed that nice domed window there (all points are on locked coordinated, as in no decimals; also, anyone who wants to see it will need to play
Dystopia, it's a map for that mod), I saved it for the night. When I loaded it the next day, Hammer had misaligned many of the vertices from as little as .1 or .2 units off, to b/w 2 and 4 units. It's not very complex, and I don't know how to model. It make me wonder how Valve created any brushes w/ the slightest bit of complexity.