MLG DEVIATING WX TOLD TO SQUAWK 7700 WHEN UNABLE TO ACCEPT HDG INTO TSTM AND PROVIDE OWN SEPARATION IN IMC.

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WE WERE NBOUND UP THE MIDDLE OF FLORIDA DEVIATING R OF A DIRECT TLH COURSE DUE TO WX. ZJX CLRED US DIRECT CEW. I TOLD THEM I COULD NOT ACCEPT THAT UNLESS I COULD DEVIATE WELL S OF CEW. THEY APPROVED THE DEV AND I MADE THE TURN. ON THE NEXT FREQ THE CTLR TOLD US TO FLY A HDG THAT WOULD HAVE PUT US IN THE MIDDLE OF THE LARGE TSTM THAT WE WERE DEVIATING AROUND. THE CELL WAS ABOUT 100 MI IN DIAMETER WITH A RED CTR ON THE 160 MI RANGE OF ABOUT 50 MI ACROSS. I TOLD THEM I WAS UNABLE TO DO THAT DUE TO THE LARGE CELL ON OUR R. THE CTLR ON THE NEXT FREQ TOLD US TO SQUAWK 7700 AND THAT WE WERE RESPONSIBLE FOR OUR OWN SEPARATION SINCE WE WERE ENTERING A MIL WARNING AREA. SO WE WERE FACED WITH 2 CRUMMY CHOICES: 1) EITHER FLY THROUGH THE MIDDLE OF THIS LARGE TSTM; OR 2) ENTER THE WARNING AREA SQUAWKING EMER AND BEING RESPONSIBLE FOR OUR OWN SEPARATION -- WHICH WAS IMPOSSIBLE SINCE WE WERE IMC. WE CHOOSE OPTION '2.' WE CIRCUMNAVED THE WX AND MADE A TURN TO THE N TO GET BACK INTO HAPPIER AIRSPACE. HAD I KNOWN THAT I'D WIND UP SQUAWKING 7700 AND CREATING A PROB; I'D HAVE SIMPLY DEVIATED N OF TLH -- WHICH WOULD HAVE BEEN EASY. IT SEEMS TO ME THAT THESE CTLRS ARE NOT COMMUNICATING VERY WELL WITH ONE ANOTHER IN COORDINATING CLRNCS. THE WX SYS WAS WELL ESTABLISHED AND SEVERE AND I TOLD THEM WELL IN ADVANCE WHAT WAS NEEDED TO AVOID IT. THEY COOPERATED UNTIL I WAS OUT OF REASONABLE OPTIONS AND THEN ATTEMPTED TO FORCE ME TO FLY INTO THIS DANGEROUS TSTM -- WHICH I REFUSED TO DO.