Those are all good ideas, but as Chrispminis said there are more pressing things at hand at the moment.
In 0.75 the game forum will be replaced altogether will something which will hopefully make communication between players more natural. The forum on this page will be relatively unchanged, and I'll probably make the forum on this page plug in to phpBB rather than code my own very complex forum.
I haven't said what I have in mind so this would be a good time to get a 2nd opinion before I code it (though changes to the DB have already been made in preparation for it).
This is the basic idea of the new game messaging, though I'm not sure about using tabs:
http://phpdiplomacy.kuliukas.com/images/message.jpg
The only other big UI change for 0.75 is a notification bar so you can see at a glance what's going on in your games from all the pages, the mail icon means you have mail in that game, the exclamation mark means you have to finalize orders, and the game's name will link to the game
http://phpdiplomacy.kuliukas.com/images/notification.jpg
I think these will be a big help with no drawbacks, but there it is just in case
Those two, a couple of adjudicator and internal changes, and some other tweaks, are all I have planned for 0.75 atm, your ideas will have to wait for a bit.
Thanks for the suggestions,