Hi there,
Yes this is possible, just be aware of the following:
1. You will have to publish these new EV servers externally and specify them in the relevant Desktop policies for Outlook Anywhere access. Also, use them for the relevant sites' office mail app configuration. Note this will not necessarily improve performance unless you move some of the users to these new servers but you said that you do not plan to be configuring any vault stores on them.
2. For the indexing servers, ideally, you should group them by location and use them accordingly.
Let me know if you have questions.