Any other thoughts on how to automate
further?

Just the auto top off. I'd use tap water for everything else or blend
it to get about 3-4 KH and GH. Don't go below that range. Discus do
well and bred fine at these ranges.

If all you after is high fry yields, then plant tanks are not good.
But if you want some breeding and the rearing, a plant tanks is good
place.
If you plan on not breeding ands the fish are mainly pets, then don't
worry too much about the tap unless it's extremely hard.

Not much else besides the auto top off, timer for the lights, leave
the CO2 on the same timer as the lights etc.
Dose your nutrients for the plants every 3 days or so. But that's easy
and just like feeding the fish.

Pruning the plants etc maybe the biggest chore you will have and
there's no automactic for that one.

Regards,
Tom Barr