One big problem was the purchase of AMC, plus Lamborghini, Gulfstream, etc. left little money for product development and the formerly ground-breaking K cars got stale.
Plymouth wasn't killed by DCX. It was in effect mortally injured much earlier. DCX only removed the life-support plug.
Maybe, but the plan to eliminate Eagle and pour those resources into Plymouth (along with plans for the Plymouth PT Cruiser, and retro-(Prowler) styled Voyager and Breeze) had been in place just prior to DCX formation. So, while Plymouth had been neglected for decades, there was a short term attempt to revitalize the brand in late 1997 prior to the 1998 "merger of equals" that ultimately, as stated, pulled the plug.
I would have loved to see what they could have done with Plymouth post 1998 had plans continued. A uniquely styled mini-van (Plymouth only) with the Dodge Caravan/Chrysler T&C continuing with conventional styling, retro Breeze, PT Cruiser as a Plymouth (car was a hit when released, may have been enough to justify Plymouth sticking around). When the Chrysler Pacifica CUV first came out, many critics pointed to the low initial sales due to the first ones being Fully Loaded and priced too high. Many folks, at the time, pointed out that a Plymouth version may have scored the "volume sales" to support the higher end Chrysler loaded models. I was working at a Chrysler dealership at that time, and the first Chrysler Pacificas that we got on the lot were fully loaded, 3rd row seat, AWD, large V6 (4.0L), leather, etc. A 3.3 or 3.8L Plymouth with FWD and 2 rows, cloth interior, would have been priced much lower.
When the LX cars finally debuted, (as a side, I heard from many sources that the RWD cars from Chrysler would have released in 02 or 03 had Daimler not put us back years in development to use their parts instead) a Plymouth version could have been uniquely styled, and played to the volume/economy market like before. A Plymouth Fury, with V6 standard, V8 optional, cloth interior, nice stereo, and similar size/shape to the Chrysler 300, would have sold. The Chrysler 300, by comparison, could have been leather only, V8 only, with AWD optional and upscale interior/stereo standard. Basically, a uniquely styled, Plymouth badged 300 Touring.
The Chrysler 200 mid-size (and Sebring before it, from 07-up) could have had a Plymouth (Acclaim) version that was 4 cyl FWD only, with manual and automatic transmissions available. The Chrysler model would be V6 Auto only with AWD optional. The Plymouth would have been the volume seller and would have made a great rental car as well.
Dodge would have been in the middle, with 4 cyl standard and V6 Optional (Avenger) and Charger would still be V6 standard and V8 optional, largely unchanged.
Challenger probably would not have been a Challenger at all, but a Cuda, and sold as a Plymouth.
New Hornet would be a Plymouth, not a Dodge. Chrysler 100 would have been made, but as a Plymouth (Scamp?)(Valiant?)
Fiat models would have been made to work as Plymouth's for the US market. Fiat 500 (2 door, retro) could still be a Fiat, but some of the other models (500L, 500X) could have been sold as Plymouth's. The 500L (I always thought) could have been the basis for a new PT Cruiser. The 500X could have been marketed as a Plymouth Duster or Trailduster with AWD.
The Voyager mini-van would still be a Plymouth and still the volume seller with the Chrysler as the upscale model.