[quote=@BCTheEntity]
3. I mean... Frieza's family line did all have at least four forms (assuming Cold was similar to his sons), but the extra forms were apparently additional [i]downgrades[/i] to their true forms, such that (using Final Hours' terminology) they'd end up having the Diplomatic form, two Combat forms, and their True form, with only Cooler having the skill to remain in his True form at all times, and only Cooler having the ability to transform [i]up[/i] from their True form until Frieza basically BSed his way into acquiring his Ultimate Evolution, though even then, the latter remained in his Diplomatic form until he actually needed to transform up. Basically, there's a certain precedent for an Arcosian being able to transform up from their True form if they succeed in controlling their True form's power, and considering that all it would realistically represent is a power increase (albeit a potentially large one depending on the owner), I don't necessarily see why it wouldn't be viable to include a Super transformation as part of a particular Arcosian character's arsenal.
[/quote]

I'm not saying it is entirely impossible for Arcosians outside of Frieza's line to gain additional forms, only that there has been no need for them. No Arcosian in history has ever come anywhere close to the power of Frieza's line, as such none of their bodies has ever exhibited a need for more than three transformations. A byproduct of this is the belief that only Frieza's line can create new forms. Also, a Super transformation is theoretically possible for the Arcosian's, much like it is theoretically possible for Humans and Namekians, but no Arcosian has ever attained such. Until recently the only form of training they have practiced as a species is to control their power, through downgraded forms or controlling their Ki. 

(P.S. I still need to see the Resurrection of F, never got a chance to watch it while it was in theaters. :( )