This won’t work really. Marketplace add-ons are validated via your xbox login. Zendesk support have informed me that it is in fact possible that sometimes add-ons may be “temporarily” missing simply because of this validation process glitching. Sign out/sign back or simply wait would be their suggested fix but this does raise the issue that the login serves as a licence validation/DRM and therefore if validation fails the modules are restricted/hidden.
Which raises the bigger issue that if something gets corrupted at your xbox profile end you could potentially lose the right to use that content permanently.
Simply having files on your HDD or backed up somewhere will almost certainly NOT be regarded as “proof of ownership” in a dispute as it could simply be suggested by support that those are file shared copies.