We do not have any integrated solution to force a certain pronunciation. However, we are developing a proper solution and the tools to force and fine-tune pronunciations. But, at the moment, we do not have any such tools available. Nevertheless, there are a few workarounds that do work in certain cases.
The main workaround is to find an alternative spelling and write a word more phonetically. You can employ various tricks such as capital letters, dashes, apostrophes, or even single quotation marks around a single letter or letter.
As an example, the "Helvetii" tribe could be spelt "HelVetIi" to put more emphasis on the "v" and "ii" of the name.