Haha, you're right, big numbers do interesting things, so the script isn't bulletproof. However, that's why I have "WARNING: common(?) sense required for tuning these parameters!" at the top of the script. Ohh. and parametric modeling is why I got hooked on openscad, that and using graphical modelers like fusion360 and freecad never really worked for me, and when you do something like "ohh, I'll go from M8 to M5 bolts" and realize you need to dig through all the sketches and re-dimension every bolt hole...

That being said I haven't had it break by just asking it for a big machine in a while, now it usually just breaks if parts don't physically make sense, like if you ask for a 10mm wide hole in a 5mm wide object, or if you don't give things enough clearance. Another one I've spent too much time debugging is when I change related parameters in a way that doesn't make sense. I've added a block of code to help troubleshoot problems, tell you what's going wrong and what you can do to fix it.

Anyways, to add something to the topic at hand. My two cents is that with i3 style printers, bigger isn't always better. They're moving the bed around, and as you scale up the printer that gets to be a lot of mass, which limits your accelerations and therefore your print speeds. However, if you need big, by all means go big.

Another thing, don't let the type or configuration of extruder be the deciding factor in your purchase. The extruder often is the easiest part to modify, change or replace on any 3d printer so don't get too hung up on the stock set up.