I think the dual fuel option is a pretty significant upgrade, like a couple grand, right? Not trying to be nosy, just trying to see if the increased efficiency is worth the cost. If you have the dual fuel option, there is no need for a backup furnace, correct? That could save $$$ on new construction.
I don't think I would skip the regular furnace. Function wise....I guess the duel fuel option would do the trick and you could use it in place of an indoor system. I am not qualified to make that decision for anyone other than me........and even then I would have to ask a lot questions. What does code say? What does the insurance company say? (fear of frozen pipes and such?) Maybe there are no issues but I don't know at this time.
What if your new stove sprung a leak and you had to wait for a warranty replacement.....how do you keep your home from freezing?
If I had to guess....I would guess that the outdoor stove, by nature, is a backup system to your main. It is just installed in such a way as to act like the main while in use. Does that make sense?
The other thing you have to keep in mind is that you will be burning wood all year without an indoor system. For some that is perfectly ok.....I personally am on the edge. My guess will be we will use our NTI Trinity boiler in the summer....or at least for part of the summer.
Do yourself a favor though and ask a lot of questions of qualified people. My father-in-law is a building inspector and he tells me stories all the time about people making decisions on there own and then he has to enforce what the code is. Even once he made a guy tear his entire house down because it was built so far off from code. (The guy thought he knew more about code than he actually did.) Lucky for him he was only through the framing side of the new build.
Boy I'm feeling long winded today!