Currently OpenMPT has 3 horizontal zoom levels in the pattern editor (lo, med, hi). The High zoom is great because you see all the columns, but if your song has a lot of channels, you lose the Big Picture. The Lo zoom is great to seeing the whole pattern, but you lose all the details.
How about combining the best of both worlds with a special zoom mode that displays the channel the cursor is currently at in full detail, but the rest in low detail?
Here is a little mock-up:
What do you think? Would it look great or confusing? What happens if the user makes a multi-channel selection?