Suggestions for Land Value- Add strategies

[Henri Meli]

I have been offered about 20 acres of land in a very attractive location in a fast developing part of a city. The price point is very favorable and the seller is very motivated to sell. The location is near a very busy intersection and there is a lot of new constructions starting in the part of town. 

The catch is that 80% of the land is in a flood zone (marked AE, AE Flood Way on a FEMA map). The seller has disclosed that information to me and I have confirmed it through my initial investigation as well. Only scattered 20% is buildable as it stands today. I'm trying to figure out how I could extract more value from the remaining part. I haven't made an offer yet. Understanding possibilities might also help me how far to go with my offer.

I have been thinking of possibilities to best leverage the given conditions of the land. 

Things have through my head such as: 

Maybe leasing portion for cell tower (?), 

Maybe leasing portion for Billboard ( ? ), 

Maybe build a storage ( ? ) ... etc.

I'm looking for more suggestions for people who might have faced this issue before. 

Any suggestion welcome.