I'm looking at some stuff about khajiit, and the reason they looked different in different games probably wasn't just because they designed them differently
they're different breeds of khajiit, but I think they just call them "forms"
the ones in Arena are most likely Ohmes, but maybe Ohmes-raht
I think Ohmes is more likely though

Ohmes
Similar in many ways to the Bosmer, although generally of lesser stature. In order to avoid being mistaken as one of the Bosmer many Ohmes tattoo their faces to resemble a feline-aspect. The Ohmes is the most common form seen outside of the province of Elsweyr, taking advantage of other races' preference to their appearance to serve in positions of ambassadorship and trade. It is possible that the Ohmes are the breed seen across Tamriel at the end of the fourth century of the Third Era.
the khajiit in Daggerfall are probably either Ohmes or Ohmes-raht as well. I think Ohmes-raht is more likely for Daggerfall than it was for Arena though

Ohmes-raht
Similar to the race of men, save for their short, light-colored fur, the Ohmes-raht may easily be mistaken as men at a distance. Unlike the many other species of Khajiit who walk like cats upon the balls of their feet, the Ohmes-raht walk upon their heels. The Ohmes-raht are most likely the breed found in Hammerfell and High Rock in the early fifth century of the Third Era.
in Morrowind there is a really significant difference from the previous games, and I'm almost completely positive that they are Suthay

Suthay
Similar to the Suthay-raht in all respects, save that they are of lesser stature and with digitigrade or beast-like legs. The Khajiit encountered in Morrowind at the time of the Nerevarine are likely of the Suthay strain.
in Oblivion and Skyrim, I'm pretty sure it's the same race for both, Suthay-raht


Suthay-raht
Similar in height and build to the race of man, the Suthay-raht are one of the most common races of Khajiit. Their coloring ranges from dark brown and orange, to light yellow, both with and without stripes and spots. Suthay-raht are often referred to as "Ja'Khajiit" by those of other races; this appellation often strikes the Khajiit as odd, said title being one of their names for Mehrunes Dagon. ("Ja'Khajiit" would literally mean "young Khajiit" or kitten, and the Khajiit call Mehrunes Dagon this "for what is more destructive than a young cat?" -Words of Clan Mother Ahnissi)
The majority of Khajiit encountered in Cyrodiil and Skyrim from the time of the Oblivion CrCIA during the Third Era and later are of the Suthay-raht strain, as well as the Khajiit found on Stros M'kai near the end of the Second Era.
I think the next game should be set in Elsweyr
I wanted Black Marsh before, but honestly I'd rather see some other Khajiit, like Pahmar and Alfiq
either one would be fine though