[jacquesm]

That's already happened, twice even.

There is 'duplo' and there is 'Modulex':

https://www.newelementary.com/2017/11/old-bricks-what-are-mo...

[thanatos519]

Duplo is Lego-compatible. A 2x4 Lego brick fits exactly onto 1x2 Duplo studs. A Duplo brick is 2x the height of a Lego brick, and a Duplo plate is 1x the height of a Lego brick.

It's fun to build large structures quickly with Duplo then detail them with Lego!

[jacquesm]

There are even ways to connect Modulex bricks to regular Lego, some people have figured out some interesting tricks.

Which allows you to take that strategy to the next level.

[AlanYx]

There was also Lego "Quatro", double the size of Duplo, for very young toddlers.

Only sold from 2004–2006, but still in high demand on the used market. Interlocks with Duplo and regular Lego.

[jacquesm]

Oh cool, never knew about that one. I do have one more to add but it's mostly technics warmed over, which is 'Znap', clearly aimed at the same market as 'Knex', which Lego at some point saw as a competitor. Since then they've come their senses, the Znap line was ugly and highly impopular, leading to being discontinued after only a year.