Find Text Attribut in Rules (potential solution for Ubercart Pay Invoice)

I've found several feature requests for invoice payments in Ubercart. (Admin creates work order/invoice, client logs in to pay invoice.)

It occurs to me there is a valid solution for this would be to expose the "text field" attribute of an order to rules. A basic setup:
*uc_varprice required
1. create Product Class: Invoice Payment
2. add Product Attribute: Invoice Number (type: text field).
3. Add Invoice Payment (product) node: Pay Your Invoice
4. in node settings, go to "Features" secondary tab and add Variable Price *
5. Create rule that explores that attribute after checkout, grabs the data, matches to an order number and sets to "Completed" status.

I've got this working all the way up to the rule on a current CRM implementation- and it looks great. To help users find their open invoices, a simple view in the sidebar shows "open" invoices (for reference). For now, I'll either write custom php or apply payments manually.

In the mean time- it seems that this is a valid feature request even without meeting this long-requested need.