Is there a diplomacy benefit to helping out a beleaguered faction?

I frequently get asked for help ( I guess I have that kind of face,  ) from Sovs in trouble with another faction they are at war with.

So we go to the trading screen and the easiest thing for me to do is throw them a tribute treaty.  Then they give me some arrogant babble about me showing respect when I am bailing their sorry asses out.  Wha... what?!?!?

So arrogant talk aside, do I get some benefit for my generosity?  Will the faction be more likely to surrender to me or broken armies seek refuge in my cities (bonus to a bordering cities pop growth for 10 turns regardless of grain)?  

Are military units and heroes going to be trade-able items in a future patch?  If I recall a certain tech still talks of trading heroes...

 'Cause then I can send my Elvish um... Tarthan Archer's to Helm's Deep er,  New Pariden instead of raw materials.