I just submitted an MR for enhancements to the CART addon.
The enhancements allow sellers to request per item and per order information from customers. Currently only textarea and text inputs are supported.
Per-order data fields are added on the Cart SETTINGS screen. Per-item data fields are added on the item-edit screen.
The order of the data fields can be changed by drag-and-drop which has been tested to a limited extent on both mobile and on desktop.
The drag-and-drop is accomplished via a couple of jquery addons that are in the view/js directory of the addon for now, but may be useful to include in the addon_common directory (or even as part of core) in the future.