Are you prepared to spend money defending your posistion (lease) ? 
That's the question I would be calculating,  . .  ..  
X amount money for litigation over the 10 yrs, what does that bring your land lease up to? Still below what similar ground would bring? You need to consult and attorney that has experence in such deals.
The risk is too great for my thinking ~

Will only add - that type of lease doesn't work here, for housing . .  . . .