It doesn't have to be a clone. The front "nose" fuselage section could be derive from An-22 or C-133/130. The tail section can be completely indigenous design (vertical and horizontal stabilizers)... Significant weight reduction by having low-drag pants for it's struts and wheels
Large mobility aircraft such as the An-22, An-225, and the C-5 Galaxy serve a niche mission where it's almost impractical+uneconomical to use multiple airframes (Il-76s, C-17s, or C-130s) to support the logistics/transport of a large amount of troops and equipment across long distances to a remote area in a timely manner (i.e. North America to the Middle East, or how large the continent of Russia is as well as how far the Soviet Eastern Block spanned). To put things into perspective, the Russian Air Force only has 11 operational An-22s and the USAF has 52 operational Galaxies as compared to the hundreds of Il-76s and C-17s that operate globally on a daily basis - if this doesn't say niche, I don't know what does.
Between the Y-20 and the Y-9, I just can't see why the PLA would require a larger airlift aircraft. As far as we know, the PLA are only interested in defending the Motherland as well as to project power into the South China Sea, and perhaps all the way out to the Second Island Chain or the Gulf of Aden - that's almost peanuts compared to the airlift requirements of the US DoD or even the British MOD. As such the PLA's mobility needs can be met by the Y-20 and the Y-9 (especially given Xi's recent military reforms to restructure the PLA Joint Logistics Support Force to effectively and efficiently respond to logistics and air mobility) to supply troops+logistics+heavy weaponry, and why I can't see the PLA requiring a mobility plane along the lines of a C-5 or An-225 to serve such a niche mission.
It also wouldn't make economical sense to devote a large amount of resources to produce a handful of planes to serve a specific niche mission, I just can't see the tactical advantage it would give. Building a plane that massive would also require new or retrofitted hangars to provide maintenance, runways lengthened and taxiways reinforced, managing completely new maintenance parts and spare logistics, readjustment of PLA operational doctrine... It'd almost be more cost effective sending a Transport Regiment of Y-20s! Its capacity might not be as large, but it provides so much more tactical and mobility flexibility to the front lines.
The role the Y-20 played in the COVID pandemic response both domestically and internationally is clear evidence that the PLA have their air mobility formula right, and why there isn't a need to develop something bigger.