Hi, I have had similar experience when I was working with Bank BRI (Indonesia) a year ago, as their Jira was local server only while I need to download many offline so I can proceed work at home, and opening a thousand tabs was out of the question.
I had a java tool provided by jira, but it was a trial thing.
But based on their documentation, we can use their API and clone the content for offline use.
Now it depends how would you like to display those data from Jira, and what features will be available will determine the duration of the project, as complex features to mimic jira web would take longer to develop. This 2 weeks is a long estimate, but if you just need a full per issue download with all the attachments and content broken down into a folder for each issue, then cataloged in a main page such
[HOME]
Issue | date | title | download assets (as zip)
shouldn't take more than 3-4 days (consultation,setup, trial & feedback) till complete.