I was thinking about it last night...
Consider the current depth of your floor joists, use one size smaller spanning the same direction as the current, these would be supported at each end but not connected to the existing floor. Only the PJ would be mounted to it and once covered no one would be the wiser. You'd also want to re/add support below them.

Or,

Place a sheet of plywood across as many floor joists as possible. This should add some rigidity.

Edit: Sorry, looking at the current electrical runs, the first idea will not work.

Last edited by brwsaw; 11/25/14 04:22 PM.