Hi Andre,
Yes you can build fully an offline app with Wappler. You can just fetch once a week or so a new JSON data / Server Connect with Action Scheduler and store it in Local Storage with State Manager and use it from there.
Other option is that Server Connect data sources also have caching build in so you can set it to very long time like a week and new data will be fetched then.
Maybe @Teodor can make a showcase and article how this is done in detail