Brandon actually just published a very interesting blog post on a possible solution using the Publish Layouts feature. This is something that could be used.
http://brandon-kelly.com/blog/custom-fields
Since neither Gypsy nor Field General is EE2 compatible, and it seems that Gypsy isn’t likely to be (Brandon has specifically said that he’s not doing it, not to mention that the hook it requires is missing in EE2, anyhow), then the Publish Layouts option might be the best bet, even though it would mean assigning virtually all of your custom fields to every channel and then selectively hiding or showing them.
Personally, I like the way MODx handles this with Template Variables, and it would be nice to see something similar in EE.
Anyhow, Brandon’s post should at least give you an idea of what you could do now if you wanted to move to EE2 sooner rather than later.