Still you should consider derive it from the print Class so the user gets access to functions as print(float, 3) etc.
(make it #ifdef configurable ?)
#ifdef sound like a good idea.
I removed it since it's a big increase in program size and memory usage.
Without the Stream dependency, I could also add write(int) and write(float).
What do you think would be better?
In another thread I replaced the magic numbers of soft serial with formulas allowing "all" baud rates. - http://forum.arduino.cc/index.php?topic=138497.0
should be possible here too. The added value is that you can easily adjust baud rates to mismatches in clocks or systems that have lots of interrupts.
I saw that thread and was intrigued.
Without knowing all the history of [New]SoftwareSerial, I'm not sure if the magic numbers weren't deliberate however. On an ATMega328p with internal oscillator, the magic numbers have proven remarkably accurate. I might try switching to your formula and running some tests.
FInally, can we expect a stripped read-only serial too?
Not at this time.