If you cannot get the firm-ware from Samsung directly, I would not even attempt to use it!!!!!
Attempting to install firm-ware from an unknown source could irreparably damage the camcorder.
Looking over the product manual, and brochure, I suspect that the difference is more than just the firm-ware that operates the camcorder.
I believe that there are 1 or 2 more ICs that are installed on the circuit board.
In fact, I suspect that the "firm-ware" is identical between the 24 and 24i versions. Having the extra hardware installed on the circuit board enables the additional features.
Chas