Devil_Hex
To increase the speed is very simple, just decrease the friction of the air that is inside the dome. I even believe Fujin can do it without the dome. And adding to the jutsu, I think it would be better for Fujin to split it into two modes: a passive form that would imperceptibly influence the winds around him, so Fujin could have a natural sensor that would put his perception on another level, and the active one would be the dome that was shown.
Minato took 3 years to create rasengan. Fujin creating that wind domain, which seems way more complex than the rasengan, in a little more than a year is just bs. This jutsu has the potential to become fujins trademark jutsu, just like the flying thunder god for minato or the raikage lightning coat. TFTC
Wind Domain sounds great but has a clear downside, namely if the opponent uses his chakra to disrupt Fujin's chakra, this is like Domain vs Domain in JJK, but if the Jinchuuriki releases a chakra burst then it is certain that the Wind Domain will spread, even any ninja who has a large chakra pool and ready to waste his chakra to counter this move