Is it possible to add the ability to use resources from your backpack? so you can repair and build with the items in there?? would make admin stuff 10x easier

Yes, this is already supported in Backpacks v3.9 if you install Item Retriever (early access).

Backpacks v3.10 will include permissions so you can restrict the feature to select players, and will allow players to toggle whether items are retrieved from each page individually. This functionality has already been implemented and can be downloaded from the edge branch of my fork. Just grant the backpacks.retrieve permission.

If you want to build and craft as admin without worrying about resources, you can try Virtual Items (also early access) which is designed specifically for that use case.

This is now available in the v3.10 beta.

https://umod.org/community/backpacks/46426-backpacks-beta-3100