Sorry for the confusion, but I don't have any T yet. I'm hoping to add one to my collection. I suppose the 2nd version (w/midrange selector switch) would be most suitable for bass, but 1st version is identical except for switch (correct me if I'm wrong on this) which could either be added (maybe a push-pull potentiometer swap or hardwire component value change) to effect for better bass amp usage.
Ok, you're wrong.
Consider the first generation a "marshall" design with a few differences (which in itself was based on the '59 bassman) with a few differences. The tone controls is a typical tone "stack".
The tone circuits for the second generation are completely different. A gain stage has been created out of the half-tube stage that used to be a buffer (cathode follower). The tone stack was trashed.
The treble and bass controls are based on a "passive baxandall" design that provides both boost and cut capability for their ranges. The middle control implementation uses an inductor in series with one of three capacitance values selected by the mid switch. The middle control determines the gain of the new gain stage, and provides a boost only action.
The second generation isn't a bad amp for bass and can usually be picked up for less bucks than a first generation.
Both vintage amps are rated at 150 watts RMS - only the fender thingie is rated at 100 watts, and that would make a lousy bass amp.