Brainstorming, please

SCENARIO:

Membership organization site -- public content and member-only content.
Anonymous users have no privileges beyond viewing content.
Current registration performed manually by admin.

Client wants an online application submittal for a contest with multiple categories, with payment through PayPal. (Site already includes winners pages/nodes -- comprised of CCK fields, wherein winner info was entered manually.) No, problem. Here was my Plan A:

MY PLAN A:

• Create new role for Applicant, with upload permissions (for contest materials).
• Create new content type for Application -- using many existing CCK fields that produce the winners pages.
• Create new contest event (already a custom content type)
• Use Auto Assign Role with currently used Content Profile (Application as content profile node)
• Contest announcement created as an Event.
• Applicant registers for the event/contest -- which sets up event confirmation (with application submittal instructions), auto deadline reminder, and nice Signup management views for staff and judges. [SignUp use optional, as I can the other things with a custom view and rules. But, the SignUp module already does it nicely, so why not.]
• Applicant registers in order to have privilege to upload files (images, audio, video, pdfs)
• Email verification with instructions for and link to completing application. [Registration link otherwise obscured.]
• After completing the online application (node), Applicant is redirected to payment instructions page. They can pay by PayPal or mail check.

[I estimated 5 hours to produce and test this on dev site then live site. Client liked.]

THE NEW TWIST:

• Now, I learn that client wants applicant to be able to enter for multiple categories at one time, and pay for all in one PayPal order (with PayPal reference to match up the site application).
• Moreover, companies need to be able to enter multiple contestants for multiple categories, and likewise pay in same process.

PROBLEMS:

• I really had wanted to avoid using Ubercart, as it is poorly supported; huge overhead (especially for a site that already uses lots of modules).
• Don't think that client is willing to spend the time for a whole shopping cart configuration. (Anyone willing venture a time estimate for that, for this task?)

Creative ideas, anyone? (No wild custom programming schemes. Using existing Drupal modules.)