Is it possible to have the logistics drones filter on greater than or less than pressure? It'd be nice to have the drones pick up canisters that are > 18 psi and deliver them around the base and return canisters that are < 11 psi. That way I can have a large central compression area.

If you're concerned with pushing similarities too close to Integrated Dynamics style utility, have another look at Botania. I'm not sure how long it's been since you last played it, but around 1.15 they added a similar functionality to the Hopperhock, where it automatically checks the mana level of items set in the item frame, and it can distinguish only between "empty", "partially full" or "full", and only for mana. So a Hopperhock next to a chest configured with a partially full mana tablet will only pick up mana tablets that are partially full, ignoring the rest.

I'm not sure if that would satisfy this feature request, but I'd imagine it working as a new entity filter type for the entity import widget.

The player would have to have their Air Canisters ejected into the world for the drones to find, which I think is pretty reasonable as it is possible to use Redstone / Omnidirectional Hoppers / Smart Chest / Charging stations to eject things at specific times.

Once that's figured out the player could use Drones to import the Air Canister entities using a filter like Air Canister (pressure=full), Air Canister (pressure=empty) and Air Canister (pressure=partial). This would limit the player to only being able to move full canisters around to places to get use, so it would either push this functionality out towards more end game or highlight more incentive for that 1.5 pressure tier.

Unfortunately, no - the functionality to filter by item properties other than direct NBT comparisons doesn't exist. There's no facility for checking specific properties of an item like its pressure value.

That is a possible feature addition, although I'd have to consider how best to implement it.