Ripping off the brick is probably a bad idea. Most likely it is not merely decorative siding, but in fact is structural and holding the house up. The "studs" you see may very well be put in there as furring strips to hold up the plaster, not real structural studs. If you're going to rip walls down to insulate, you're better off ripping down the plaster and putting in new drywall. Cheaper and faster. Also, bear in mind that brick is saving you some money on your homeowners' insurance--it's quite fire-resistant. It may even be helping keep your home warm more than you know, as bricks, mortar, concrete, rock are all heat sinks. That is, they absorb heat (including sunlight heat) during the day and re-emit it at night, helping to modulate the air temperature from extremes. I'd be real happy to have a brick or fieldstone house here in New England!
The mold & condensation issue someone else mentioned is likewise a very real problem. If you rip out the plaster and put in a series of vapor barriers before insulating, that might help with the condensation issue, but then you need to consider what sort of structural timbers are in the house's interior--wouldn't want trapped water vapor to condense onto structural timbers over the spring and summer evenings.
In our very elderly house, to avoid the water vapor issue, we ripped out plaster and installed boric acid-treated cotton insulation made of recycled denim scraps. Maintains water vapor permeability and insulates quite well. It was not cheap though.
Instead of replacement windows, have you considered something like
Energy Panels? They are just a couple layers of fancy plastic film stretched into a framework with little clips to hold them into the window frame, and they work a bit like storm windows, but they are cheaper than replacement windows. We aren't allowed to replace our windows due to historical society restrictions, but we were allowed to put Energy Panels on, because they can be installed on the inside part of the window, don't significantly damage the frame, and are not visible from the street. It's helped an awful lot--my house is nice and toasty in freezing weather, and I am burning much less wood than last year.
Edited to add: What type of heating system do you have? Forced air typically feels slightly chilly at 68F to us thin-blooded folks, but radiant floor heating feels toasty warm even at 60F. With new floors, you can probably install radiant floor heating underneath as an add-on, and it will likely feel warmer without actually being warmer. I realize that doesn't seem to make any sense, but it's sort of, if your feet are warm, everything else feels warm. My brother, who has radiant floor heating, keeps his thermostat at the same temp I do, and I have forced air--yet in his house I am warm, and in my house I need a sweater or two.
Oh yeah, your parents never told you "If you're cold put a sweater on"