Thought 2: My "house rule devised without a clear statement of the problem or idea of how this would solve it" radar is pinging. Perhaps I'm wrong and there is a specific problem that is being solved economically by this rule... but I can't imagine what it would be. I am now wary of what other house rules this DM may drop on us without warning.
Yeah your Spider-Sense would be correct here. There is nothing solved by this at all. There's no equality between the three different things. Feats can be taken and have no meaningful impact on balance, or even easily make a character weaker. It's rare that they're a significant boost in power. The fact that the OP is legit terrified of the two Feats which make Concentration checks easier makes me wonder how much he's even played 5E, it's such theorycraft stuff. As someone who has played casters/buffers for most of 5E, I really haven't had to make many "clutch" concentration checks. When I worked out my "build" for my current Druid I was sure I'd be grabbing Warcaster by 4th, but... nah mate. Despite basically continually running a Concentration spell, and losing a couple, it really hasn't been that huge a deal. Like big whoop, all it really does is give me a reason to cast another, more situation-appropriate Concentration spell. Or just work around the issue by not using Concentration spells in a specific encounter - not like I don't have other good spells!
Likewise, multi-classing can enable some pretty powerful stuff (though barely better than a single-class with the right subclass, note), or it can kind of gimp you. It all depends on the player and the build.
And rolling for stats? What method? Many of them are likely to make you worse off.
Like, if I was terrified of power-creep, I'd feel like an idiot giving out this choice, because people can build plenty-outrageous characters without rolling for stats, so if they "need" a Feat or MC option, they're just going to select the one they "need".
