Saving as DWG - What to do with rogue SHX files created in the process?

We are generally a DGN shop, but on occasion have to send a DWG to some other agency. When this is done, a number of SHX files get created in the default workspace system folder and then, they are added as available fonts. And since this occurs across a large group of users, this can create a false sense of what fonts can be used. and since any user can save a DGN as a DWG, this can spread across the entire user base. We want the user to be able to send the files with any needed SHX fonts so the receiving persons will have a faithful translation, but how do we isolate these from ending up in production?

Is there any way to easily suppress these fonts globally. It seems that the fonts created will vary depending upon what file is converted and what fonts it uses.

And when we get a DWG, how do we know which shx fonts are delivered with MicroStation as opposed to ones possibly created by a save as DWG process?