This had actually occurred to me.
When I was starting this thread about what I was building I actually called it a SIP-like-planter as it doesn't really meet all the criteria to be a true SIP.
I did look for something to use as a floor instead of the perlite, but anything that came up either didn't work or was prohibitively expensive.
This is a total experiment, and it might crash and burn, but it should be fun!
If I start to smell a problem through the watering tube my plan is to first put a bunch of H²O² down there, and then to drill multiple holes around the res and switch to a modified wet dry cycle, never fully filling the res. This mimics the way some pots I used to use work, with a watering port at the bottom.
They grew great plants, but we're only 10 litres and got rootbound quite quickly.
It might be too late by then, but we won't know for sure unless someone tries it.
I'm planning to grow an auto in there, and I don't know how that might change things though.