Even with the microwave delete I bet the cabinate where the microwave would be will still be there so you could always add one if you want or, if you ever want to sell it. The microwaves that come with TT's are usually the cheap ones anyway.
As long as your building a home don't skimp on the insulation in that either. It might cost more at first but, it sounds like you plan to stay and a well built, well insulated home will pay for itself in the long run.
A home that sets the right way to the sun can save money in heating and cooling cost too.
You may even want to plan to add solar or wind power to your home some day. You may not want to right now but in case you do some day in the future the time to think about where it would go is now before you build.
It's nice to see someone your age with your good money management ideas. Congratulations