Prefered Types

Hello, i have an old system where used implicit casting
float<->integer
numeric<->float
numeric<->integer

I want define implicit casts, but postgresql don`t know cast priority
now postgresql have PREFERRED flag, but only flag
I can`t define prefer level like
Integer=0
Numeric=1
Float=2
Maybe
text = 2 or 3
and other to define My prefer cast more detail than just flag
i understand what it more dificult tuning, but more flexible
now i can only create duplicate operators like
numeric+integer, integer+numeric, integer>numeric.... and many other
What can i do? Can i wait for prefer flag changed to prefer level?

--
С уважением,
Зотов Роман Владимирович
руководитель Отдела разработки
ЗАО "НПО Консультант"
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mailto: zotov(at)oe-it(dot)ru