Corinnguard
Hero
Racial Substitution Levels worked by replacing 3 of the 20 class levels back in 3e, well before WoTC came up with subclasses for 5e. For 5e, they probably would replace subclass levels because of their thematic feel.Even if you are right the solution should be simple and easy: to create a racial substitution level.
For example replacing with other catrip or a feat. Or the catrip light would enjoy a free metamagic feat.
Wouldn't it be easier to create racial subclasses for the classes? PF1 did this for a couple of their classes.