You don't need to mod your Dreamcast.
True there are newer models that won't taked burned discs, but they are extremely rare. (I think manufactured after October 2000 doesn't work, but the only "known" version that doesn't is the Sakura Wars special edition. Good luck finding one of those!)
The only thing you really need to worry about is your cd-burner, since over 50% of the cd-burners on the market cannot burn most bootable Dreamcast images.