A question preoccupied me for some time.
It is technical possible to put some DF-21D missile with big VLS-lauchers (2x2 of the universal VLS-launcher of 052D) on board of the 055? For four missile you would need the space of 16 ex universal VLS of 052D.
What would be the impact to have DF-21D on board of type 055 destroyer?
You're talking about putting something the size of a SLBM into a DDG hull, which even after extensive (read: uneconomical) modifications to its hull design to accommodate such a thing, it will stick all the way up to the bridge level if not beyond; and when it lit its stage one motor (it's a cold-launch design), you can kiss all the armored windows on the bridge and just about all the radar and antennas on the superstructure goodbye - essentially, before it even hits anything, you've just took a 055 (the launch boat) out of play.
If you don't believe me the size difference between DF-21D and all the other ship-borne, VLS-friendly missiles, just go and watch the 2015 parade, and see for yourselves.
Seriously, DF-21D got adopted isn't because it's a smashingly good idea but rather a "when you don't have a choice" one - even now, without ASBM, China really lacks in capability to target the USN carrier battlegroup. The goal of the exercise isn't so much about actually hitting it, but rather as a deterrent through the presence of such capability. The US would say in public that such a thing won't work, but just look at how much effort they put into the missile defence upgrades to counter such possibility, as well as the USN carrier battlegroup no longer do the show of force cruise off Chinese waters like back in 1996, proves the value of ABSM systems like DF-21D. Still, such a thing is destined to be land-based, it'd never be deployed on a surface ship due to the reasons mentioned above, and won't be deployed aboard SSBN which the PLAN has very limited boats to begin with, and they're all needed for SLBM nuclear strike package.