Turning Zone wide mob spawning into shard-only visible per client

[Shin Noir]

Howdy,
If a dev more familiar wanted to give me their thoughts on the difficulty (or a suggestion of how to tackle this), it's hugely appreciated:

I'm messing with a server called TheoryQuest. Inside it, I'm planning to remove Track for all classes (including Ranger). This opens up the ability for not spawning every mob in a zone as EQ normally does.

Pros: You can't use MQ to see every mob up.
Pros: Less load on the client since less mobs on zone.
Cons: Running through a zone means more packets need to be sent to the client to inform what mobs are up.
Cons: Dev time

How tough would it be to make EQEMU not provide all spawns to a zone at load in, and instead load mobs as you get near to them? Is this a huge undertaking, and I may not want to bother with it? Any shortcuts I can maybe take?

That's about it, thanks for taking the time to read my post.