I've yet to see a company publish a system that works that way and is successful in getting sales.I mean, in 3.5e we had wizard and fighter as perfect examples of that.
one had no spells and lot of bonus feat slots, other had spells and fewer bonus feat slots.
The typical drawback of classes systems or low class systems is that you struggle to make abilities and features of different archetypes equal in power or scope that they are all valid choices when creating characters. So players and game Masters who really want to dig into specific archetypes typically are not able to. It's typically a struggle to balance a barbarian's rage with an assassin sneak attack and a paladin smite if they're all equally choosable feats.