There is little the modders can do about the most serious AI and diplomacy issues in ETW. Many of the stuff appears to be hard coded, or is not working, or we do not know how it works. So the best we can do (speaking for all mods) is to find workarounds.
The main features in TROM are changes to unit stats and recruitment. Overall, this should lead to a better composition of AI armies and a more realistic feel of the battles. There are also some changes to unit morale and unit formations that should help the AI making better decisions on the battlefield - but here we are hampered by the limitations of the ETW engine.
One of the things we did in the campaign was to increase the money for a few factions (especially France and the Mughals) so that their AI puts up a better fight. As far as I can compare with vanilla, the Mughals are holding up pretty well against the Maratha.
Yes, you will see naval invasions, but probably not more than in vanilla ETW (again, this appears to be a code issue and CA has announced they will address it). In any case, I've seen Prussia invade North Africa and Britain invade Hannover by sea. I haven't seen any cross-theatre invasions, but I believe this is due to ETW bugs, so nothing we can fix yet.
As for diplomacy: this submod by Yarkis (
http://www.twcenter.net/forums/showthread.php?t=273322) seems to tone down the useless declarations of war by minor nations. You can also try the AI submod for APE:TI... it should be compatible.