There are so many request here on this forum for new things, I fear it will prove impossible for Wix to judge the commercial validity of them all, let alone develop them. Now, in non-Wix Code environment, 3-rd parties have the possibility to wrap their app into a Wix environment (like 123Forms).
If Wix could open up Wix Code for third parties, it we be a huge plus. Then others, who already have written a stable editable grid, a scheduler, whatever, would be able to wrap a Wix layer over it and offer it at a price in the Store.
Wix Code always reminds me of Visual Basic: starting from the front end, easily hook up a database, etc. But the biggest hit for VB were the components (VBX, later OCX) that 3-rd parties could write and sell. Without it, it would have been far, far less successful.
I would gladly pay for it.