Of course not all these are required to run MODx, but PHP in FastCGI with suEXEC makes my life a bazillion times easier.
I totally agree with your list of requirements, but I have questions about suExec. What are the advantages of running PHP this way? So far my host has not switched over to suExec, but it seems like it's only a matter of time before most hosts do (for security reasons).
The only interaction I've had with suExec installations has had to do with limitations imposed by it. For example, you can't set PHP environment variables in your .htaccess file when you're running suExec. I habitually turn register_globals off and set compression and whatnot in my .htaccess file, so I guess I'd have to use a php.ini file instead (and my host would have to allow this, which right now they don't).
We now have about 15 accounts hosted on OneWorldHosting, and they have been receptive to our requests for server setting changes in the past (when we first started, they rewrote their entire Control Panel system when we complained that mod_rewrite didn't work properly with it). So if there are solid benefits of running suExec (other than server security, which is a given) then maybe we can give them a little nudge. We have used many other hosts in the past, but nowadays we stick with OWH because they have proven themselves to be extremely reliable and their tech support is exceptional.