I would first off require citizens who want to assume responsibility for building in a noted, but not accurately determine flood zone to be educated as to the dangers and all that shistuff, then, as long as they're not in a floodway, build with no flood insurance(their choice).
If the BFE has not been determined since there has been no detailed study, then it holds that the floodway has not been determined either.
Basically, I feel the owner has the right to benefit from his/her land the same as everyone else.
Bear in mind that construction in a floodplain can adversely affect adjoining owners due to the potential for decreasing flood storage volume. Often it is insignificant on the individual basis but can cause considerable flood elevation change on a cumulative case.
From your comments, it appears the issue you have is really not with FEMA, their flood maps, or the NFIP in general. What it appears to me is that you are in disagreement with the local agency policies on development within a floodplain. FEMA does not regulate how local development occurs. Rather this is the authority of the local building officials.
Note that those who do build in areas subject to flooding can purchase flood insurance policies. The cost of these policies are not only dictated by the building specifics such as elevation above the 100 yr flood.
The costs of flood insurance are also dictated on the community rating in the NFIP program. If a community is proactive and works to address a wide number of NFIP criteria, then the citizens of that community will benefit by lower rates. Some of these criteria are things such as maintaining a high order benchmark system in the affected community.
Basically the NFIP and FEMA encourage the local community to be educated on those things which will reduce the loss of property and lives in catastrophic flood events. This is not only in the interest of maintaining the value of improvements, but more signficantly in protecting public health and safety.
I'll say that once again: "protecting public health and safety". If you disagree with that mantra of your local community, then good luck in your endeavor of trying to change how your building officials and local elected officials have been addressing development within a floodplain.