As far as I can tell, the TZ offset code can be simplified by eliminating conversion from timedelta to int and back in utcoffset() and dst() methods of time and datetime objects.

The only reason for the restriction that I can think of is that some text representation of datetime only provide 4 digits for timezone. The behavior of formatting functions, can be preserved while allowing fractional minute offsets elsewhere.

On the other hand, given that this issue did not see a single response in more than a year, it seems that there is little interest in fixing it.