This will be the third year https://www.raidpulse.com/
will use Maprun. I've assisted from the Maprun setup perspective and developed an Excel application that will grab results as runners upload and match these results with the registration list, allowing, after any adjustments, overall results to be issued. The organizer uses flags with attached laminated bits that include a QR code as a backup tin case any team has bad phone GPS. In addition runners have a sheet where they need to record a three letter code at each control which is also validated.
As you thought, using good control locations which have properly been checked with GPS worked just fine, Not sure if you are thinking of doing this without flags - I think it would work but more susceptible to phone issues and arguments afterwards.
I think the main issue is people showing up for their first race and not having spent the time to properly setup and test the app on their phone (detailed instructions are sent out). I had one team the first year that couldn't get Maprun to work - not a surprise as every time the phone asked if the app should have access to location data they clicked "NO"! In general the teams doing the 8 hr were much better prepared while the 3 hr teams less so,
Last year we added a small (three control) test course just around the arena. This was useful to let people make sure things were set up properly as well as us validate that the MapRUn Name they provided when registering was the actual one they were using.