Sounds liked funds are tight. You can reduce your total investment if you sell paper lots to a land developer/home builder. In summary you would do the leg work on the front end to ensure the deal is developable and prove the property profitable to a developer/home builder. So step on would be to get a home builder/developer on board to take down your lots. Step two is to get a concept plan/plat approved by the city.
Every city does their concept plan/plat process differently, however I find it strange that a city would require you to have complete construction documents prior to platting. Typically studies (traffic, drainage, utilities) are required at the planning stage along with a plat/concept plan but not construction documents.
You may be able to get 14 -16 lots on the deal unless you can reclaim some of the floodplain. What are these size lots selling for in this area? What are home builders paying for lots? Do the numbers work out?
Also If you want to stay in the deal and make some more money after you sell paper lots you could stay in the deal to manage the design and construction for a fee.
Best of luck to you!
BR