That is a good build, pretty similar to one I have thought of, with exception of taking points away from warhorse handling and scale armour, and putting more points in mounted fighting mastery and chainmail.
But while there is a freedom to have unlocked a majority of both skill trees, to be good certain skills would make it very restrictive. What about formation, equipment maintain, first aid, and/ or drill? Placing skill points at the Chivalry and Footman skill trees would leave very little for the other minor skills, which I personally IMO find can be detrimental in fighting/ campaigns without one or two minor combat skills unlocked.
If there was a suggestion for me to make, it would be to allow shields to be used with those who unlocked mounted fighting mastery or lancing, but don't give any special abilities or powers that the Footman shield tree benefits from (so just wield and block with them), helps keep Chivalry soldiers from looking to other trees to access abilities from their own trees.
That's just my two cents, I frankly don't have any idea what the devs want to do with that ability.
My build