Listen to Leon.

Robert

Listen to Robert.

I am not a pro, but a very serious hobbyist. In the last 12 months, I have
done both: bought and built.

I built 3 interior frame and pannel doors and bought one exterior fiberglass
door. The original exterior door was a beautiful 40" wide 150 year old
door.. it just leaked like a seive. In a northern NY climate it was just not
working.

Without a doubt, it was a compromise, comfort v.s. style.

Building closet doors to match the rest of the house was quite a bit of
effort, but the margin for error interms of fit/flat/square are nearly an
order of magnitude larger that for an exterior door.

Maybe if you were in a mild climate where the impact of leakage was minimal
I would go for it, but it sounds like weather tightness big requirement.

-Steve