I think it would be great if HubSpot had a feature that allow for the display of old/sent newsletters on the front-end, where anyone can browse through and read all our past newsletters, just as you display blogs in pages.
At the moment Hubspot’s suggession is to genrate webslinks for each newsltter and manually load the links on the page were you wish to display it, not practical.
So this should be consider as an idea for development. I think this can be achieved either by having a module that pulls all the newsltters onto the page or have it available via an API call.