In the current campaign I'm running, players used a variant of the "Focus and Foible" system that I believe was published in "The Way of the Wicked" for Pathfinder.
The original was pick a stat to make 18, pick another to make 8. Everything else is rolled as 7+1d10. I tweaked it so the Focus...
It's not a huge deal, but it does mean they get more focus in Wisdom which is one of the three primary saving throws in the game. Since Charisma is a popular dump-stat, moving abilities away from it might be construed as an advantage of sorts.
"Vicious" is the 5E equivalent of "Keen" - it's a flat bonus that increases steadily instead of exponentially with other crit-related benefits, and also can apply to any weapon, not just slashing or piercing.
If they actually have an arrangement with WOTC where wizards is covering the refunds, this is fine, but if it's just passing the buck this is unacceptable.
There are a few class abilities that provide healing as well: usually self only, but sometimes others (Lay on Hands), so you'd also need to decide what to replace those with.
Is it possible that the phase "The spells must be of a level for which you have spell slots" and similar are in the context of that specific class and aren't meant to override any reasonable interpretation of the optional multiclassing rules? Correct me if I'm wrong, but there are no multiclass...
Ummmm....yeah. 3E multiclassing was a also a fair bit like 1E dual-classing, but the XP penalties when your classes drifted apart made it hew a lot like 2E mc'ing as well. But you're right, like 3E, 5E removes most of the punitive elements in favour of elegant integration of abilities...