Instead of "freeing up" land based fighters to defend the near seas, you could just buy more land based fighters in the first place. Instead of supplementing land-based sensors, you could buy more land-based sensors in the first place. The point of carrier-based fighters isn't to supplement land-based fighters, nor is it to supplement land-based sensors, except as a necessary and less than ideal compromise of the primary role of a carrier. Defending the homeland from an attack is in general less than an ideal use of carriers. And land-based fighters are plenty enough to protect UAVs and MPAs patrolling in the near seas. A naval air wing certainly doesn't guarantee air superiority just because it's flying from a carrier. And we're not talking about these UAVs flying thousands of km from shore; they are flying hundreds of km from shore where land-based fighters have plenty enough endurance to escort them around. There would also certainly be more of them available for escort duties than a carrier air wing.
I don't tend to think of buying carriers primarily for home defense as a "balanced" investment, so much as it is a just plain "bad" investment, even in these pseudo-power projection scenarios where they supposedly force multiply land-based assets that could instead be force multiplied by other land-based assets that could be gotten for much cheaper. Pierside carriers for home defense is a concept I've never read anywhere else on the internet except on this very forum in this very thread.
By 2030, there would be ~14 055s, 46 052C/Ds, and 79 054A/Bs. Why is this an unreasonable number? Note that even by then the PLAN would only have 60 large surface combatants compared to the 87 that the USN has right now.
You expect a 12,000 ton cruiser to replace a 7,500 ton destroyer as the mainstay production unit for large surface combatants going forward? You are even more optimistic than I am. As for LCS variants, any such uparmed/uparmored frigate variant that incorporates at least an 8-cell Mk 41 and 2 quadruple launchers for Harpoon, LRASM or other missile will be at the very least a match for the 054A, though not likely for the 054B. But this is certainly a short term interim solution for a real frigate replacement, which the USN is actually looking at as part of its Future Surface Combatant program; this does not include the LCS, but will look at what types of ships (large and small) the USN will need in the 2030s timeframe.
Why would you limit tonnage comparisons to just surface combatants like cruisers, destroyers, and frigates? By doing this you erroneously elevate PLAN's overall effectiveness compared to the USN, as if a cruiser/destroyer/frigate comparison that compares closely somehow implies equality between the PLAN and the USN by 2030. Such a "fleet" would most certainly NOT be comparable to USN when you include carriers, subs, fighters, etc.
Why not? China intends to become a mature major global naval power by 2050 if we're going by their white papers. 140 is only about halfway there, and they have more nearby water that they have to actively defend given the number of neighbors they have, so maybe we should expect an active fleet with more tonnage.