Then this, as I've stated above, would be a function of the PLAN's future AShM development rather than an inherent limitation of the J-20.
You cannot magic away physics. The J20’s bays just doesn’t have the volume to carry decent sized strike weapons because that’s not what the J20 was designed and built for.
Even if there was some sudden quantum leap in propulsion and explosives technology to allow you to achieve decent range and explosive yield with a projectile small enough to fit in the J20’s bays, such technological breakthroughs are hardly going to be limited to air launched anti surface weapons. SAMs, SSMs, BMs etc would also benefit, effectively cancelling out the gains.
What you are suggesting is akin to using a Maserati to move house. Sure, you could have a go and do a bad job of it while risking significant damage to your premium sports car, but why would you bother doing that when you have perfectly good vans available?