On the subject of Ysalamiri...

Honestly think the ruling here is quite fine as it is. Ysalamiri are meant for singular player characters and can nullify a force users main advantage technically within an instant.
To have these rules and making them hard to obtain, requiring people to constantly care about them, also ensures that they're not some regular threat on a daily basis, which they honestly were neither in Star Wars Legends.
Sure, Thrawn utilized them as a breeding ground for Spaarti cylinders on Wayland, but that's pretty much it and troop production isn't necessarily a strategic factor within the RP in a way, where we would need to argue about Ysalamir in that terms of category.

So yeah, to answer your question, I'd assume that one Ysalamir on your main character should be in most cases enough and also the most reasonable to manage if you want to keep it fed up. Maybe one or two more for some important NPCs maybe, but they're not supposed to be spread over an entire army force for obvious reasons. So definitly would require quite a lot of RP with a good reason behind it.

Ysalamiri were very rare in usage in canon. Most people had 1 or 2 of them under most circumstances. Thrawn was a bit of an exception to this, given Zahn created Ysalamiri for the purposes of his novels. In fact where Spaarti Cloning is concerned, their only real use was when trying to create an adult clone in 15-21 days without incurring madness, which is very much an edge case scenario.

The ruling is pretty clear on the limitations of the fact that Ysalamiri are dreadfully difficult to keep alive once removed from their native habitat and that special care and attention needs to be taken in keeping one alive. The rulings intent was to maintain that same rarity on JvS as we see in Canon, with a more unspoken, but clearly intended, limitation on how many a single writer could have.

Jenia and Nem have definitely capture my feelings and understanding of the ruling quite well to be honest in terms of "how many is too many". At the end of the day, the RP acquisition should always be about making a compelling story that adds to the narrative and can be read not just as "well here is my post/s proving I/someone acquired X item" but as a story about how your character knew they would need one for "reasons" and went to Myrkr to collect one, with maybe some road blocks or failures, before success is achieved. Otherwise it's just a fetch quest, which are never really fun to do in games and feels boring to read and write.