We discussed this a bit in IRC. In the current version, Simon wants to ensure that no two zoom levels are too close to each other. I think this is why 100% zoom got eliminated and the jump was from 70% to 200%
I disagree with this, I think that no two consecutive zoom levels should be too far apart. Furthermore the common integer zoom levels, as well the zoom where the level fits horizontally and where it fits vertically, should be included.
I think I'm in favour of more fine-grained than Simon here (Simon wants only one zoom level by default between 1x and 2x zoom while I'd propose more than that), but apart from that Simon agrees that this could be a sensible solution.