Since then there's arrived wide consensus role-playing aspects make poor balancing mechanics.
In other words, don't expect something like this to reappear in official material. (House ruling it appears to be rather straight-forward, however)
I'd say Ad/DisAd would be the easiest way, and most consistent with 5e
I always liked the spellcasting distinctions between the three orders of magic, i.e. how Black Robes levelled faster and got access to higher level spells sooner, but had less spells overall (IIRC), with the situation reversed for the White Robes. IIRC, a black robe got access to 9th level spells at level 17, and a white robe at level 19. Red robes used the PHB spell advancement table, and got acces to 9th level spells a level 18.
I was disappointed when they didn't use this in the later versions of the DL campaign setting.
This idea is around in my head since the beginning. I really like the Advantage/Disadvantage in the spell attcks, but what about the spells that aren´t attacks?
Close, in 1e Black robes did gain spells a lot faster than red or white, they gained 9th level spells at 13th not 17th level but since 13th was also the rank for master it meant that only 1 black robe could be level 13 or higher. The others gained them at level 15.
But yeah, I always liked that system. I was introduced to D&D through DragonLance, and to this day, I kind of assume wizards will wear alignment-appropriate robes, regardless of the setting.
Regards.
Team DL forever, baby. Or at least, Team Weis & Hickman DL forever. There's some real chaff outside the main books.
It's been a long time since I read the DL Adventures hardback... 13th level seems awfully low now.