Want to create partitions of a MySQL table and change the charset of new partitions
Partitions have in their syntax the option to have different engines for every partition, but this is not (yet?) supported.

Having different character sets for different partitions, however, may not make sense as all of them should have a common data structure. It is also not supported. Please understand that the charset is a property of a field, not of a table, and that the only reason you can configure it for a table is to set a "default".

If you want to create partitions for archiving, that is a good call, as it makes easier to delete old ones. Be aware of MySQL partitioning restrictions.

If you want to change the charset of a field in an online fashion, I recommend you to use any online alter table tool (I think that MySQL 5.6 does not allow for online charset alters, but I may be wrong) like Facebook's, Percona's or Shlomi's.

As an addendum, if at some point you need to mix different charsets on a field (I have needed it in the past as an intermediate step for having invalid charsets), you could set the type of the string to binary type instead of text (BLOB instead of TEXT, VARBINARY instead of VARCHARetc.). Binary strings do not have encoding information.