First of all, thanks for this awesome new game mode! It's actually one of the main reasons why I finally joined the 21st century and bought a smartphone

I was wondering how you acquire basic lands in Planar Conquest mode? Or how you add them to your deck, because I seem to recall removing a basic
Swamp from my deck earlier when I first unlocked some multi-lands, but now that I'm getting ready to move towards a 60-card deck (and beyond, eventually) I can't seem to select it anymore?
I might just be missing something obvious though

On the other hand, I do suppose basic lands are a difficult / non-obvious case, so maybe they were missed somehow (aside from the removing-from-Aether-selection thing)?
If so, I would suggest maybe handing out 1 free random (plane-appropriate, but not Commander-color-appropriate) basic per win (probably without notifying the user)? That would allow you to eventually get enough basics for whatever you want to do (decks for alternate commanders, 250+ card decks, using a healthy dose of basic-land-fetch cards without running out eventually, ...).
I don't know if their
Exile value would have to be lower than regular commons (1 per win won't make you super-rich), but I would certainly suggest keeping them
Exile-able, so you can get rid of the ones you don't need (as there are so many different ones, they could clog the card lists quite a bit

)
Bonus suggestion : Chaos fights give full-art basics (from Un-sets etc) instead of plane-appropriate ones.