A little late to the party, but:
I wouldn't use racks, but a load of
https://produktprogramm.tanos.de/en...iner/T-Loc/Sortainer-T-Loc-SYS-Sort-IV-3.html as the organizing storage for your stations. The individual drawers can nicely be pre-packed at your base and as they can be swapped between the 'drawer rack' systainers within seconds (while being protected from accidently being pulled out of them completely, toppling and spilling their contents, when opening in a hurry) they can quickly be mixed and matched to give you a stack of easily accessible drawers (that have enough space even for bigger stuff and with the organizer options can also hold smaller items like syringes and whatnot in an easily accessible and organized manner) that can quickly be tailored for a particular use, with the ability to re-arrange them in case demand changes.
On-site stations could quickly be refilled by bringing replacement drawers (a stack of empty SORT/3 and a cart/roll for transportation) for the out/low ones so one dosn't have to replace a whole systainer with multiple drawers when only one needs refill (or even the whole stack) while not having to occupy the station to shuffle individual contents into place with patiens waiting. Having defined drawer types makes it easy for a station to order 'we need one #2 and two #5' when they see the need of a refill coming, way easier than having to list individual materials.
Speaking about refilling: I think I would have one SORT/3 extra per drawer type with refills to always have 3 ready-to-go replacements for each type of consumeable drawers (and one whole additional station in case things go south, which I have seen happening when I did medical services for events some ~25 years ago). In case you need more material (longer or back-to-back events) where it dosn't make sense to bring loads of pre-packed refill drawers I would suggest using normal systainers (one or a set per type of drawer) to carry bulk-in-bag of
everything needed to refill that certain drawer configuration, so these are refilled on-site, leading to returning to base with all stations basically being ready to go to the next job and only the bulk storage systainers in need of refill (when using the usual slow time at the end of an event to clean up things). Everything labeled (both the drawers and the storage systainers with the refills) per type should make it obvious which drawers belong to what bulk-in-bag storage systainer(s), should give you an easy and quick to operate system.
Maybe also think about
https://www.tanos.de/en/products/new_products/mobile_workshop (the hole pattern MDF tops replaced with with solid, water- and disinfectant proof sheets) so you could setup work areas where/when you need them, eg. to create a backstage station where you can set removed-from-systainer drawers currently in the process of being refilled at a comfortable working height - should you do events that are more... rustic or open air where there are only tents.
Add a bunch sys-cart (for places where you have even, stable ground) or sys-roll (for rougher terrain) to move stacks if systainers around quickly without having to carry.
I wouldn't recommend the older sortainers, the SORT/3 are IMHO better since they're easier to open (bigger, easier to operate lockbar), have pull-out protection (though easy to intentionally overcome when you actually
want to completely pull a drawer), are quicker to un-/stack (as of T-Loc), keep the drawer contents in place even when being turned upside down (as the drawer top is closed by the flat, closed top of the slot it goes into) and there is only one type of drawer so they can be re-arranged freely.
Hope this hepls.
