if you're using a logical progression to decide on MC options, the first thing that you know for certain is what high level abilities you give up to MC, which is why I started with that. That trade-off may make you decide it's not worth it. After you've decided that, then you can start looking at ability delays and synergies.
Except that deciding that something isn't worth it because of what you'll miss out on at level 20 seems dubious to me.
Here's an example: suppose I'm building a glamor bard with a few levels of sorcerer for metamagic, some attack cantrips and defensive self-buffs. I'd like to go Bard 17 / Sorcerer 3 to get 9th level spells eventually, and let's say I've settled on Bard 5 / Sorcerer 3 with the actor feat as a breakpoint, because my concept is a slippery infiltrator who uses disguise self and expertise and advantage in deception to get places where he's not supposed to go, and then uses spells like Suggestion and Hypnotic Pattern with subtle spell to control the situation. My ASIs and feats will be Actor, +2 CHA, Alert, and Resilient CON. I'm giving up my 5th ASI for metamagic and 9th level spells, but I'm happy with that trade.
If I want 9th level spells eventually, I have no choice: I've got to go bard the rest of the way. But this means that my last three ASIs come at levels 11, 15 and 19. If instead I take Sorcerer 4 at level 9 then switch back to Bard, then I get ASIs at 9, 12, 16, and a bonus one at 20. That means that for all but two levels of my character's remaining career, I've got one more ASI under my belt than I would otherwise. At level 20 I'm sad because I don't get my 9th level spell. But for almost the entire campaign before that, I have a really useful feature I wouldn't have otherwise. And, ok, it doesn't come for free: I'm delaying all my other bard features by a level each. But it's certainly possible that by sacrificing a high level feature for one level, I'm making my character stronger for most of his career.
(By the way, I kind of want to play that character now)