Someone at my local game shop recommended Sun Quan, Lord of Wu as an option for a new commander in my mono-blue flying EDH deck.

What exactly happens should I get him out? Horsemanship is essentially flying but land bound. Since my creatures now have 2 statements on them that says they can't be blocked except be creatures with the right keywords, what exactly happens there?

It would essentially mean your creatures are unblockable unless the opponent has a creature with flying AND horsemanship to block (which is pretty unlikely in EDH).

But it is EDH so stranger things have happened. I've played a shadow/wall deck before.
I think i may have to find a Sun Quan now just for the ridiculousness of that combo.

I have thought of building one too. I like the idea of having something crazy like a Lorthos riding a horse (or an army of horses) past whatever army is trying to block.