There's also the issue that the current build menu is pretty cramped, and some players don't like the build menu getting thiccer to accommodate the striders
shipfac would be the biggest issue here, it's already a cramped factory with just about every role taken and it needs to take in 3 more striders.
There's also the issue that most striders just inherently belong to striderhub. their defining characteristics are pretty much just "strider". It would be pretty out of place seeing paladin or detri in the build menu of any factory.
Personally, the best way to shuffle them would be like this:
(it still runs into issues with striders being out of place)
Athena => planes
Ulti => cloaky
Dante => JJ (flamethrowers are the most common in JJ)
Scorp => Spiders
Funnel => Shields (to avoid spiders getting 2)
Scylla => Ships (only place that has subs)
Reef => Hovers
Shogun => Amph (amphs are usually havier than hovers, and shogun is heavier than reef)
(ISSUE: amphfac is underwater)
Merlin => lveh (nowhere else to go)
Pala => tanks (nowhere else to go, heavier than merlin)
Detri => specials tab, next to the other superweps.
In the era of site mods, you can always make a mod that does this and see if players prefer this over base game
EDIT: the vehicle factories are also in a pickle as there is no vehicle striders