the plastic piece your talking about is flimsy. if you attach a handle to it it will probably break. you'll have to drill into the actual door frame underneath which is metal.
2003 Rubicon, 4.0L, 5SPD, Custom 4.75" lift, 33" MT Baja Claws
1999 SE, 2.5L, 5SPD, sold it
PM me for wheeling in and around Northern Illinois