Yes, many semi subs being scrapped for pennies as there are too many rigs on the market, the cost of conversion would be high with new regulations though. Doubtful if it would be cost effective in this day and age as "hull" a small percentage of overall cost, Chinese shipyards cheap and they build good hulls, during the last boom they were building a lot of hulls which would be floated to Singapore and the like for topsides.
The last FPSO to leave China was for Shell, a round rig, hulls were originally built for drilling rigs, very stable, DP3.
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