So it's a 50% chance of an Ultimate that won't cause any problems and 1 in 7 chance of a Mega that won't. This is based off your own words, and the definition of 'dark' and 'corrupted' digivolutions already laid out in this thread, as well as canon instances of dark digivolution.

After the first time, I don't think many would be keen to work with Guilmon again, and I can guarantee at least Marabumon will view her as a threat to the other Knights. Can't speak for the others, admittedly, nor what Magnamon will be like at that point. I'm pointing out now you'll have to accept at least that much.