Depends on the motor. The "inherent balance" of an I6 doesn't mean it's perfectly smooth. A Pentastar equipped Wrangler is noticeably smoother feeling than a AMC 4.0 equipped Wrangler. I'm still not convinced I6 is definitely the way to go, or that it will somehow "improve" packaging. Ford, GM, Hyundai, and many others have no problem packaging twin-turbo V6 engines (in both longitudinal, and transverse applications), so I'm not sure why it's such a problem for FCA. Many of the engine bays the Hemi fits into now are already pretty tight length wise. Toyota's 2JZ family engine (3.0L class) are around 31" long, and the AMC 4.0 was around 32". That's 3-4" longer than the current 5.7 Hemi engines. Additionally, other automakers have tried the "modular" engine family thing before, and it usually ends up with some particular variation of the engine being a compromise. Like the GM "Atlas" engines, where the engines got worse and less competitive with each cylinder lost compared to the "main" I6 engine.