Its possible with a lot of work but the problem you would have is that a lot of the new features require the performance gains from the new OS and so although it would work it would be painfully slow.
Xperia X10 (Traded In) > Xperia Arc (Dev Handset) + Xperia Ray (Back-up Phone) > Xperia Arc S (Retired) > Xperia S (Retired) > Xperia T (Retired) > Xperia Z (Current)
Xperia Tablet S (Current)
Developed the Dark10 series (X10 + Arc/Ray/Arc S)
Helped in development of Timescape mod's (X10)
Helped in Graphical development of FXP ICS (Arc/Ray/Arc S)