Fighter/scout. I can think of better combos to use in Gestalt.
If you're going to do a lot of mounted combat then I don't think its that useful to focus on TWF. You won't be making full attacks often.
But you could put in a level of barbarian. For Lion totem Barbarian which gets you pounce.
Now a skirmishing pouncing spirited charge. Thats something nice.
I would take away the repeating crossbow still. You need to fire it with two hands in order to use the reloading crank.
Its a bit of a buzzkill I know.
I'd do it like this:
1 Lion Totem Barbarian/scout EWP (double Hand crossbow), Hand Crossbow Focus, Point Blank Shot
2 fighter/scout Mounted Combat
3 fighter/scout Mounted archery, Versatile Combatant
4 fighter/scout Precise shot
5 fighter/scout Ride-by attack
6 fighter/scout Spirited charge
8 fighter/scout
You may want to beg your DM if you can have the 3.0 glove of storing which was about 3000 gp IIRC. You can store and retrieve your scimitar as a free action. That gives you the two hands you need to relaoad your hand crossbow. And hand crossbow focus will let you reload it as another free action.
TWF isn't really going to give you anything since its likely you will be either slashing people or shooting people in a single given round. Unless your plan was to on occasion wield 2 crossbows and go Johnwoo. That can work pretty well too. With the glove of storing trick. A friend of mine has managed to build quite an effective character like that in one of my campaigns. But unless you're gonna do that I'd say go for versatile combatant. That way your crossbow shooting won't provoke from the guys you're meleeing with.
Oh and you'd wind up using a regular scimitar instead of a greascimitar. But I really doubt the feat is worth the gain. Oh and stay away from ranged disarm. Its bloody bad. You wind up disarming at a -4 and there's no way of getting the improved disarm bonus through the feat.
And I'm afraid you can't select Shot on the run at lvl 8. The entry in the scout class says that you still need to meet the prerequisites of the feat. So that one's still open.
Edit: I overlooked the posts about the animal companion. You can shift point black shot to lvl 4 and precise to lvl 8 freeing your first level feat for wild cohort.
