As this is a game set up for competitive play...

I'm assuming any sort of scenic basing that alters the physical proportion of the model is a bad idea? (Ie conversions to make troopers prone, ruins on bases that rise te model height).

In the armada tournament rules you can't modify any gameplay aspects of the model (eg the base). Since Legion is heavily dependent on actual LOS, I'm assuming we basically need to assemble the models straight out of the box with little if any modification.

Any thoughts?

yeah.. idk.. i'd be somewhat cautious about modifying the height too much. I too love to customize my minis.. i usually use a layer of cork on my bases to make road / cement bases but can't because of the firing arcs on the big bases.. slightly annoyed by that.. my go to basing technique is pretty much out..

that being said besides a few game night kits, i don't really plan on playing in big tournaments so.. who cares!! have fun, that's what the hobby is all about!