The crucial problem that limits our knowledge of our own galaxy, and prevents us from working out how and when it formed, is our inability to measure direct distances to distant stars, and to determine their proper motions. If we could get accurate parallaxes and proper motions for every star in the galaxy, we'd have things completely wrapped up, and surely we'd be able to figure out galaxy formation.
All this requires awesome angular resolution. Luckily, this is just what should be achievable using space interferometers. A number are on the drawing board: most of them will be quite capable of measuring a parallax distance and a proper motion for every star in the galaxy with enormous precision. Just think what that would mean for astronomy!
In addition, these missions would find planets around other stars, image the central regions of AGN, and measure the proper motions of other local group galaxies. This is too good an opportunity to miss: you have to persuade all these high-redshift types to forget about staring at infinity for a bit and concentrate on the galaxy on their doorstep: if they cannot figure this one out, surely they are doomed in their attempts to study things at the edge of the observable universe!