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"
г.Иваново, ул. Палехская, д. 10
тел./факс: (4932) 41-01-21
mailto: zotov@oe-it.ru