Mosquito B.Mk IX was the first Mosquito bomber with high blown engines. It could carry four 500lb bombs in the bomb bay (maybe one under each wing, I don't recall), but not a 4,000lb bomb. The Mosquito B.Mk IX 'Special' was modified to have an enlarged bomb bay enabling it to carry a single 4,000lb 'cookie'. It was basically halfway between the Mosquito B.Mk IV and the Mosquito B.Mk XVI. The Mosquito Mk IX really isn't needed in AH.
The first Mosquito bomber built in the factory to take the 4,000lb 'cookie' was the Mosquito B.Mk XVI. The first Mosquito bomber to carry a 4,000lb 'cookie' was a Mosquito B.Mk IV 'Special', but the single stage, less powerful Merlin 21s on the Mk IV made it a struggle to carry that much weight.
If I wanted to get functionally complete coverage of Mosquitoes in AH, I would suggest the following:
Mosquito Mk II - First fighter powered by Merlin 21s or 23s (less powerful than the Mk VI's Merlin 25s) that lacked any bomb capacity and had an earlier, weaker wing. Guns identical to the Mk VI. Available in 1942.
Mosquito Mk IV - First bomber version powered by Merlin 21s, could carry four 500lb bombs in the bomb bay and had an earlier, weaker wing. Available in 1942.
Mosquito Mk XVIII - Fighter-Bomber with a 57mm automatic cannon in place of the four 20mm cannons, powered by Merlin 25s, bomb bay taken by the cannon but underwing ordnance possible as on Mk VI and with 1,000lbs more armor protecting the engines and cockpit. Available in 1943 or 1944, don't recall.
Mosquito Mk 30 - Late war fighter with high blown engines, no .303s, larger ammo load for the 20mm cannons, no bomb bay though a 500lb bomb could be carried under each wing. Available in 1944.
Those four would complete the Mosquito lineup to all reasonable degrees. Single digit, didn't see use things like the Mk XV aren't really needed. Nor is the relatively low production, halfway step B.Mk IX/