please don't tell me ... I'm trying to figure it out for myself!
I like that attitude! It's a refreshing change from all the "Please give me the circuit" type posts from people who want to get a passing grade without doing any work.
Anyway, I'd like to point out a couple of things you may or may not be aware of, and the simulator won't reveal:
The first is thermal effects. As a rule of thumb, a transistor's vBE decreases about 2mV per degree C,
for the same collector current. For a given temperature, increasing the vBE by about 26mV doubles the collector current.
The result is that if we keep vBE constant and increase the junction temerature by about 15 degrees, we can expect the collecter current to double. Since increased current will generally lead to higher temperatures, there's a nasty positive feedback reaction. This can result in thermal runaway, where temperature and current increase until the device burns out.
Normally we only worry about this with class AB output stages, however it could also be a concern with a 2 transistor mirror. For example if the output transistor of the mirror has vCE=20V and it starts with 5mA collector current, it will be dissipating 100mW. That's enough to cause significant heating in a small device like a TO92. Without doing the math, I strongly suspect you'd end up with a burnt transistor or two.
If you're using dual (or quad) matched transistors, this is less of a problem. With both transistors on the same piece of silicon, the temperature difference between them will be much smaller.
The other thing to watch out for is that in simulators, all the transistors are perfectly matched i.e. every 2n2222 is exactly the same as every other 2n2222. In real life they can differ quite a lot. On the other hand, I suspect that datasheets are often overly pessimistic regarding the spread of vBE.
All of which makes emitter resistors seem like a good idea as they can:
a) Increase the output impedance (your original problem)
b) Provide thermal stability
c) Make the circuit much less sensitive to component mismatching
Interesting amp design, btw, especially the output stage. ;-)