Sure, but you'll have to combine WT's and WV's policies, and fit them within the global wikimedia-wide policies (of which there are few, mainly to deal with userrights and crosswiki issues).

I'm thinking more of the smaller projects rather than the main ones.

For example the Italian wikivoyage has several of the policy pages written in German, which clearly should be translated/modified when moved over, as one can hardly have a policy in a language different from the one the wiki is written in.

Snowolf