Nice. Thanks for sharing.
However, maybe you're already aware of this but I think folks should be warned: it increases the pool replenishment rates everywhere. HE units may now be recruited more often.
e.g. Imaldris Riders are recruited by stables with a replenishment rate of 0.07...
Code:
recruit_pool "Imladris Riders" 0 0.07 1 0 requires factions { egypt, } and hidden_resource rivendell
...which means 1 new unit available every ~14 turns.
But your walls give a further 0.99 to that rate...
Code:
recruit_pool "Imladris Riders" 0 0.99 0.99 0 requires factions { egypt, }
...and rates stack, so if you have a stables then your replenishment rate in that settlement is now 0.99 + 0.07 = 1.06 --> every turn the pool increases by 1.06 units --> a new unit is available for recruitment every turn, instead of every 14 turns.