Can you actually convert Spain to Nahuatl in EU5

[ploppy]

Instead of standard colonization, what if you play Castile, rush Mexico, and flip all of Spain to Nahuatl?

The plan:

Rush exploration, take the Aztec lands, and ship thousands of Nahuatl pops back across the Atlantic into Toledo and Madrid.

Crash Catholic clergy loyalty, let Nahuatl zealots take the capital, and accept their demands to flip the state religion.

Replace the churches with pyramids, run Flower Wars into France to keep the Doom counter down, and aim for 100% conversion of the peninsula.

Is this even possible with EU5's mechanics?

Pop shipping: Can you realistically move enough Mexican pops to Spain to trigger religious rebels without going bankrupt?

Instant death spiral: The second you flip, your religious unity hits 0%. Can you survive the immediate civil wars while all of Catholic Europe attacks you at once?

Hardcoded blocks: Does the game actually let a major Christian nation flip to a pagan faith through rebels, or does the engine stop you?

Has anyone tried this level of cheese yet, or will my king just get sacrificed five minutes after the flip?

[rubish 1]

game rule to let you switch religions is there