The 2K Sports titles have been bit by this a little; the Reel Maker feature which allows players to create highlight reels, edit them, etc. was DLC the first time it was included. People were stoked to pay for it as an add-on. Shortly thereafter it was included in another title; I'm remembering NBA first, then NCAA or somesuch.
Someone noticed that the size of the DLC in the 2nd title was only 108KB, meaning the application was already on the disc. Whoops.
However, honestly, if there was only 3 or 4 months difference between the titles, why should people who bought the earlier released title have to pay for something which the (barely) later title includes for free?
Honestly, if I was faced with this, even if I COULD include the feature on the ROM, I'd probably make people download the full thing just to avoid the accusation.