I had this idea: when extracting mescaline from cacti, could we first saturate the water with NaCl to take the osmotic pressure to the roof? This way the cells would be destroyed more easily.

If my calculations are correct, the osmotic pressure of saturated NaCl(aq) will be:

Solubility of NaCl = 359 g/L = 6.14M, then

P = iMRT = 2*6.14M*0.082(l·atm/K·mol)*298K = 300.22atm

Does it make sense?

test it.

pondering theory is an exercise in mental masturbation
the only way to really know is to experiment.

No it makes no sense at all;

First off, your aim is not always to destroy cells but to diffuse the mescaline out of them. This is what an acid cook mostly does; diffusing molecules out of the plant tissues.

Second, how do you plan to destroy cells with osmosis with salt saturation?!?! You MUST at least know (that is, since you feel confident throwing formulas and calculations around) that in a hyperosmotic solution the plant cells will shrink instead of swelling and bursting (as you plan). You need a hypotonic solution to theoretically swell and burst cells. But plant cells are pretty resistant to hypotonic solutions because they contain cellulose walls and cellulose is one of the toughest materials.

You can destroy cellulose with termites ~.o

Or with Thermites!

I think that simpler methods are already giving one maximum efficiency, like grinding ,freezing and thawing, boiling. If one is so determined to break the cells or have maximum surface, one could grind/blend the material, boil it, freeze-thaw it, boil it again and -as with masturbation- "repeat till full release/repeat till satisfaction is achieved".

SWIM tried boiling a handful of termites along with cactus during the acid cook but nothing happened...