Ohh, so it’s a repeater limited to a single row, basically?
We’ve got something like that in 1.6, if you set the minimum and maximum rows in the repeater properties to 1, it’ll remove some of the repeater-specific parts of the UI, like the “add item” and “remove item” buttons. I might need to set up your custom input in my dev site to see how it differs from that, and if we can squeeze in more improvements based on that into 1.6. 