Good afternoon,
It is possible to redirect visitors having a specific user agent as MSIE 8.0 with Cloudflare's new Rules. You can set up a rule with a HTTP field for this user agent (see http.user_agent). Other field options are available here: Fields reference. You can filter them by "Headers".
Thought process: It's explained in the answer itself. From all the options I considered, this seemed to me to be the simplest one. Additionally, it is possible to customize the cache for this case.