It's very, very common for actors to reprise a live action role as a voice role, but I only know of one or two cases of the reverse.
Kinda apples and oranges because there are very very very VERY few instances of characters that originated in animation being adapted to live action to begin with, whereas the other way around is WAY more common.
Basically there's Harley Quinn, Saw Gerrera (who, incidentally was originally conceived for a live action project that never went ahead) and that's about it. Everything else was either done VERY poorly and thus not a particularly good example (see: The Last Airbender and pretty much any live action anime adaptation...though most of those originated in Manga, so it depends on how hair-splitty we get!)
Saw, for example did not feel like the same character, but they compensated for that by intentionally making him an older, damaged, broken and half crazed shadow of his former self. You can't really do that with Ahsoka....well, you
can, but just probably shouldn't.
With Harley, it's a little different since typically most of the later versions of her after Sorkin were different versions of that character, in different continuities (the live action one for sure) so it's not really taking over the role, it's a very specific adaptation of the character in a totally new setting and stories.
I can't quite see Mark Hamiill playing a live action Joker. Trickster yes, because he's done that already, and later also did the voice for it in some of the cartoons. But Joker?
Well his version of the Trickster on The Flash a few years back was about 90% Joker, so in a way he's all but done it already.
Even so, it's not really a valid comparison since Joker didn't originate from BTAS, he came from the comics and there were numerous live action and animated versions of that character well before Hamill took the role (and has been many since.)
As I stated before, with Ahsoka there's literally only ever been one actor to take that role and it's a character that was made for that medium and there's only ever been one version of Ahsoka. So you don't get the same leeway one might with other such characters.