HI Uday,
yes you can very well achieve the task of changing the properties of the fields by doing some coding in .htm of the view.
Yes what you were saying is correct.. redefining GET_I_S_XXXX method eats out your performance..
The approach of modifying the .htm would not affect performance as this page gets triggered every time before the o/p gets displayed..
pls follow the link
http://scn.sap.com/docs/DOC-29972
If you have Any doubts pls ping me !!