Every time theres a battle in EU3, just load up the correct TW game and play out a custom battle: M2TW, ETW, NTW, S2TW
Paradox could add TW-style battles to their games. It's just, that kind of micro management doesn't really fit with the Paradox games. It would certainly have to be an optional feature, primarily for SP. In a large MP game, it probably wouldn't be suitable, as most players wouldn't take any part in each battle.
@Musty, the AI in the TW series is getting better. Long gone are the RTW days, when I could use a single regiment to take down a whole army.