Probably would spoil the simple elegance of the design.
A simple receiver for AM from KHz through 30 MHz is
fairly easy to do but probably not with the uBITX layout.
Think wider, or variable, IF filter bandwidth, and having
built in noise blanker, AGC/AVC More audio gain, and
manually adjustable input RF tuning. Maybe even a
roofing filter to help shape the IF. Higher power audio
output would also be nice. For higher frequency coverage
a series of down-converters could be added ahead of
the RF input. Same thing for VLF and below if the user
was interested in that.
But that is not what the BITX20 discussion group is for.
There are on-line groups that specialize in this.