Sometimes the advice for cubelets is to stick to three or four archetypes but here’s a template for a full ten-archetype cubelet.
Put in twenty “mega-glue” cards that are each good in exactly four archetypes each (for example five per color and the card should be good in all four archetypes of that color and not good for other archetypes).
Then for each of the 45 possible pairs-of-two-archetypes, put in one card that’s only good for either of those two archetypes and bad in the eight other archetypes.
Then finally for each archetype put in three cards (maybe signpost uncommons) that are only good in that particular archetype.
That makes it so every archetype gets 20 cards (three that only it wants, nine that one other archetype wants, and eight that four other archetypes want). We’ve figuratively fit 200 cards in a 95 card deck.
Now here’s the trick. You get to scry 1 three times before you draw your card for the turn. (It’s scry 1 thrice instead of scry 3 so you can’t know what your opponent is gonna draw. But to speed it up you can place the cards on top of each other as you reject them and then place the deck on top of them instead of strictly putting each new rejected card under the previous one.) That means there’s a 61% chance of drawing a card relevant to any one architecture you want (and much, much higher if you’re building a board that combines two or more archetypes).
Now, since in a normal cubelet you have plentiful access to five-color lands, you can’t just rely on color to gatekeep it so that each “mega-glue” cards are “only” useful in exactly four of the ten archetypes. Maybe you could if you changed the land rule but otherwise you’ll just have to be very careful selecting the mega-glue cards.
I had some ideas for how to change that land rule. First I was thinking that maybe a white card becomes a Dimir land and a Selesnya card becomes a Grixis land or I dunno. Cards can make the mana they aren’t (five-color lands make colorless mana and colorless cards make any of the five colors). I thought it was gonna look ugly to leave the cards face up so first I thought maybe I’ll just discreetly scribble on the color wheel on the back of cards to indicate what the lands are. But then I didn’t wanna do that. Even if the cubelet is built out of draft chaff, in the apocalypse when there are no more card printers these cards are gonna matter to someone. So how about this? Each land also has the Meteor Crater ability, i.e. they can make colors you already have in play. That way you don’t need to peek as often underneath to remember what colors your lands have.
Or, maybe they are five-color lands but you can only have so-and-so many permanent colors in play and maybe some limit on non-permanent spells. (The following is a li’l too overwrought to be a refined final rule but just to think out loud: you can have permanents of up to two colors in play and cast instants/sorceries of up to three colors per turn but they count against each other so if you already do have two permanentcolors in play you can cast instants of those colors and up to one extra color per turn.) That way if your Rakdos board gets wiped you can switch gears and try to build up with Selesnya or Gruul. Season to taste (i.e. maybe allow the arcs or wedges in an arc or wedge set).