Yeah, if you are looking for a bye week filler go with Gio. Long term? Ab-so-frickin'-lutely rather have Trayveon. Bengals have given the highest usage to one back in league in Mixon I believe.
They use Gio for a pass catching role which he is great at. However, we know he sucks between the tackles. Perine is a plodder and primarily used on game day for special teams purposes which is why he is active over Trayveon.
Trayveon will be 100% active this Sunday because they finally have need for his skill set. Do not forget this kid led all of the SEC in rushing yards just last year.
This reminds me and is very similar to JaMychal Hasty's situation in SF. The difference is there is a lot more certainty as to how long Mostert will be out. With Mixon there has been little to no information, which really makes me wonder about the severity. If any news leaks he is out for a prolonged stretch you could have yourself a gem here.