This is a sensible idea. Basically it moves all champions to be henchmen...unfortunately Altar isn't a one that has issues with XP problems given they can go on their own quests.

Hm neat idea I must admit. And it would remove the double fame to balance all that questing..

Very interesting idea. I like it.

Interesting idea, but would end up making it a trait everyone picks - maybe not for balance, but for funfactor.

The real issue is heroes are boring because it's such a pain to level them, and units are so much more efficient. 

I'd use a three-pronged solution

Adventurer's Guilds no longer one per faction (but the +1 Fame per Turn Adventurer's Guild would be a wonder, perhaps have a world wonder equivalent that is buffed).  Perhaps the one per city building could require Ereog's Journals as a tech?

Reduce the XP split, maybe adjust XP gain so additional heroes in a stack don't split the XP in half/third/quarter, but instead reduce the XP by making the monster count as a lower lvl monster (maybe -1 level per additional hero in stack?)  That would be a more gradual penalty, and you wouldn't get punished so hard for using 2 heroes to kill something that needs all your heroes to kill.

 At one point the XP split was to be taken out (was changed last minute before beta 1) , perhaps we should try that in the next beta and see what happens, then adjust it back if it leads to problems?

Maybe leave the 1 per faction and have it give you more experience for stationed troops. Add a +1 xp chance for every fort city for stationed troops to account for training, at a high enough fort level... level 3 or higher or something.

Maybe the Adventurer trait could make it so the Sov always gets full XP, even if the heroes' XP is split (Sov would count as a hero for splitting, just would not suffer the split).  Although I would prefer it if All Sovs Always got full XP (except vassalized ones).  This is a midpoint between no splitting and always splitting, and it makes the Sov more special and able to attain more power even if with other hero/es.

Flat out removal would seem OP.

As some have mentioned though, reducing the XP penalty for Adventurers would be interesting.

A neat idea for a new World Wonder, instead of a bland 1 per faction building.