If they do, I'd update the Inkscape Portable launcher to automatically configure it for the platform's font directory on each launch the way I have the GIMP Portable launcher work. The latter is likely easier and more likely for them to add. To be able to do it in the future, the Inkscape developers would either need to add support for dynamically added portable fonts (those added via Windows' AddFontResource API) or add the ability to look in an alternate directory for additional fonts.

Sadly, Inkscape does not have a similar method to add an additional path for Inkscape to pull fonts from.

The GIMP Portable launcher automatically configures this for the platform's portable font directory on each machine so that GIMP can use the platform's portable fonts even though GIMP itself wouldn't see them being dynamically added. Within GIMP, however, you can set a specific directory for GIMP to look in for additional fonts at the app level. Some other apps, especially cross-platform apps, have this same limitation.

Apparently it will not recognize fonts that are dynamically added to a running Windows instance, only fonts specifically installed to the Windowsonts directory. I've looked into it and Inkscape is incompatible with portable fonts.

Inkscape font guide