While those rules aren't the greatest and only really matter in book 5, you've got some of them wrong. The mounts and equipment is just a one time payment. By the time we got to this part of the campaign out Kingdom was making so much money that we basically had three armies in the field for each army the enemy had. So while it was expensive it was a problem we could just throw money at and solve.
Is that an Errata? Because in the book example, it wasn't like that. See Centaur's outrider consumption 5 (they are paying for their bows, weekly, and they are even paying for they "horses", as they count as cavalry), or the Boggard's consumption of 14, which includes the healing potions. Bassically, every saturday night, if they haven´t used the potions already, they drank them, and you have to pay them again in next Sunday morning.
Not to count that it cost you the same 10BP to give potions to a group of 10 elite rangers, than a horde of 5.000 legionaires, or the fact you can raise as much armies you want, as long as you have money (or even if you don´t, as they don´t disband if they don´t get paid, they just get a minus to morale). So, while you need a certain kindom size to raise a unit of 5000, you can raise 5000 units of 1000 if you want, march for a week, crush the enemy, then disband them. Plus there's no hint about how good the soldiers are. You can raise lvl 1 warriors, or lvl 10 paladins. The only difference is you have to pay more. It doesn't even matter if you haven´t build a single barrack, ever, in any of your cities. You can have armies, without having barracks, or castles, or even watchtowers. You can have cavalry even if you don´t have stables, and so on.
Plus you only swim in BP if you go the "magic item factory" route. Without spamming magin items to sell (for example, if your DM doesn´t want or allow "ye old magic shop" in game), then the economy simply can´t support having an army.
In my opinion, it was a huuuuuuge dissapointment. The first two books were great, the 4th was ok, but the 5th was quite bad, in my opinion. YMMV, of course, but the OP is asking for opinions, and mine is that.