It seems that some considerations have to be made before you choose a light to give your wife for her intended purpose.
First it needs to be dependable. To me, this leaves incands out. I've had my own personal emergencies that required a light and have, more than once, wound up cursing because the lamp had blown. LEDs are the king of the hill for this. You NEVER have to worry about a blown bulb or a shock popping the one you're using.
Second, you said that she will typically use it for 20 to 40 minutes. I would have to say a regulated light for constant brightness that won't dim. I like the A2, but due to reasons stated above, I'd again go for an LED.
Third, if you go with an LED, you would have to consider that your wife will probably be laying the light down while she works and then picking it up again, so heat will have to be a consideration. Both incands and LED lights get hot. With an LED you can go for a light that is kind of small, but has some mass and keep it at a conservative bias like 500mA. 500mA will get you a very healthy dose of light output, long runtime and mild heat.
Lastly, you said that she will probably have the occassion to have to go looking for someone. This would suggest something that offers a decent amount of sidespill, but also has a good throw. I'd say something with a 27mm reflector or larger.
LED lights have some distinct advantages. The regulated ones don't dim as the batteries drain. You don't have to worry about blown bulbs, and they can be had with at least two levels of light output.
After considering the above factors and the fact that you want to stay away from 123's, what I would suggest is something along the lines of an Aleph I head with a nice T bin Lux III running at 500mA (Nexgen converter). This will get you very good throw and a nice sidespill, along with minimal heat and a good runtime.
For the body, I'd go with a Balrog three cell body. Although this body was designed for 3X123's, it works equally as well with 2 AA's.
I'd cap it all off with a McE2S tail switch. This will give your wife two levels of light. Low level for those up close tasks and an insanely long runtime, and a high level for really reaching out.