Here's an idea
- By default the hive does not have access to shields. This prevents invaders and caravan guards (if applicable,) from bringing them and keeps you from having them at embark or making them yourself.
- Cut learn rate not to zero, but just to an extremely low amount (say, 1/5 of the normal.) This is a matter of balance for when you want to fight intruders rather than use traps for everything like some kind of insectoid gnome. Chitin tends to not hold up well against.... Anything. Except blunt weapons which in my experience seem to habitually glance off unless the user is stronger than normal. This then offers wasps some semblance of intelligence, using shields from enemies primarily as defense against ranged fighters.
- Any shields they get need to be looted. And due to an abysmally slow learn rate, will be extremely clumsy with them without danger rooms or lots of live combat training.
- All of the above means that while wasps can use shields with some oafishness, they A. Cannot produce them or use them in sieges, B. are handicapped to the point they require considerably longer than anyone else save possibly warlock minions to become decent at using them, and C. need to fight or capture enemies to even touch one.
Another two points to this, player controlled units will
not use shields unless they are told to do so or their uniform specifies it and sieges of course can only bring what the entity has access to without using reactions. With such a severe handicap that offers only a faint hope of any usefulness and the fact all invader shields tend to be made of rather heavy materials, many would likely find it easier to just scrap the shields rather than use them at all (some may do so on principle to save on weight, keeping thier soldiers light fast at the expense of protection.) However, it still provides an
option for those who do want to use them, without cutting shields out in a very arbitrary manner or forcing them to have to do some raw diving to allow wasps to use them themselves.
They are, after all, intelligent (or their hivemind is.) Better to have them just have a noticeable disability rather than flat out crippling them with an apparent case of "wasp does not understand the arm board at all or why food uses them," especially in larger fights and against archers, and to get them the player must face the enemy or trap and disarm them for the things.