Talk you out of it? Okay.
Where will you keep your stuff?
Where will guests stay?
Do you not need any alone time? Tiny houses mean you will never have any alone time to speak of, unless one of you leaves the house.
Will it be kept on a trailer? My Dad used to haul mobile homes, and some of the issues he said would come up were: wind catching the side of the house and shoving them all over the road (if not tipping them over- Wyoming winds are horrifying to deal with), certain routes were off-limits to them, potholes raised absolute hell, stuff shifted around inside the house, no matter how tightly cupboards were taped and secured, inclement weather (flooding, snowdrifts, high winds) can mean the floors will be quite cold, and if it's on a trailer there's very little room for SHTF supplies.
That's all I can think of right now.