This is very ambitious, unique, and gorgeous setup! Thanks so much for sharing. I look forward to seeing more of the aquarium aspect of it as well... perhaps even more unique things such as a rock waterfall or something? I wonder what else can be done with that hang on back filter if you use that - I know there's people who have emersed plants and stuff growing in the HOB filter.
Or have you considered having a canister filter (not sure where to put it) and build some kind of rock waterfall and have the filter output go there so it trickles the water down? Might look neat with the oasis theme
And finally, what's an oasis without a sand waterfall inside the tank? You have the sand already