This would be a useful addition, especially for WordPress sites that are used to distribute Android applications. I think a configurable attachment whitelist would make more sense than hard-coding individual formats. Administrators could then allow formats such as APK, ZIP, RAR, or PDF depending on their site’s needs.
There should probably also be some safeguards around APK uploads, such as MIME-type validation, file-size limits, and permission checks, since allowing executable file formats through attachments could introduce security concerns. Having those controls while giving administrators the flexibility to enable specific formats would make this feature much more practical.
I’ve done something similar before. I’d probably build it as a simple order form rather than trying to make the whole thing work like Excel. Let customers enter the quantity, calculate the subtotal automatically, and show the final total at the bottom. That should be much easier to manage in WordPress and still give customers the same basic experience.
