Are you looking for a theoretical build or a practical one?
Theoretical build, it looks like you've really got the bases covered in terms of number and variety but there are a few tricks for more. Add in the Magic Initiate feat for more. If your cleric domian is nature you get an extra druid one. bard magical secrets can pick up more. Warlock 3 for Tome can get you 3 more for any spell list (and they are Chr based instead of whatever).
Practical build. Hmm. well, there's a diminishing return for cantrips - you can only cast one at a time, and many do variations on the same thing. So I don't think you need to go to those lengths to still be the character with "a cantrip for every occasion".
Well, Warlock 2 with Agonizing Blast will be the most pure cantrip damage, though depending on the rest of your build one of the SCAG cantrips to attack with might work best.
The other combat choice could be Vicious Mockery, when imposing disadvantage for one attack is king.
Some rather useful cantrips:
Druidcraft (Drd)
Guidance (Clr, Drd)
Light (Bard, Clr, Sorc)
Mage Hand (Bard, Sorc, Warlock)
Mending (Bard, Clr, Drd, Sorc)
Message (Bard, Sorc)
Minor Illusion (Bard, Sorc)
Prestidigitation (Bard, Sorc, Warlock)
Shillelagh (Drd)
Thaumaturgy (Clr)
So, let's take a look. Warlock 3 (Tome) will give us 2 cantrips (EB, Booming Blade) plus 3 from any list Chr flavored. Let's take our druid options so we don't need to restrict armor. So Shillelagh (based on Chr), Druidcraft, and Mending. I like cleric 1 for medium armor prof, so that's Guidance, Thamaturgy, and Light. Sorc 1 keeps us Chr focused so we're not going crazy with multiclass requirements, giving us Mage Hand, Minor Illusion, and Prestidigitation. That leaves us Message off our list, but we could pick it up a number of ways, like another Warlock level. With Shillelagh to use Chr to attacks and Booming Blade, as well as Eldritch Blast, we're set for basic damage. We have good AC, and a large nujber of useful out-of-combat cantrips. And we can focus on Chr, and have a 13 Wis we don't need to pump. We're moving as "they guy with the cantrip for everything" already at 5th.