hello, im the guy from the regigigas leak and im giving you more information because im going to get fired (not telling you why).
this is a list of ideas that are being worked on gamefreak for the gen9 regional forms and some can be scrapped so after saying that, lets start with this (sorry for my bad english)

bouffalant
chimecho and new evo
deerling and sawsbuck
whismur, loudred and exploud
tangela and new evo
shelmut and accelgor
roselia and new evo
patrat and watchog
pansear and simisear
pansage and simisage
illumise
girafarig
blitzle and zebstrika
scraggy and scrafty
tympole, palpitoad and seismitoad
ledyba and ledian
petilil and lilligant
phanpy and donphan
volbeat

yeah, i know most regional forms from this list are gen5, the reason:

gamefreak knows that most loved galarian forms are from gen5 (for expample, darumaka darmanitan and yamask) so they are experimenting with gen5 mons so they can finally bring gen6 regional forms in gen10

see you soon with a list of gmax forms being added in the dlcs