I've been playing around with the modded 57, and I think the loss of transformer has made the mic less of a general purpose mic.
to get the mic to be general-purpose again you'd have to put a passive filter in series with the output to tame the high end, and low-end proximity effect.
the cheap transformer cuts the bottom off, and distorts it so that you can still hear the harmonics.
it also has a natural roll-off because of the way it's wound which does a high-end cutoff kind of thing.
you can always place the transformer in a box, and put a switch in there to put it in and out of the signal path.
you could also do an H-type high frequency filter with a couple of resistors and a film cap... to tame the high end.