It might have a decent chance of working 10 - 15 years ago, but it's not gonna cut the mustard now.
With the recent tectonic shift in US-Sino power and influence globally, there is no incentive for China to accept this nebulous "Chinese Commonwealth". The DPP under William Lai has already shifted to light blue in terms of advocating for status quo, peace talks, respect for ROC etc. All three major political parties in Taiwan are now continuing Ma Ying Jeou's 3 Nos policy, i.e. the risk of Taiwanese independence is close to a statistical zero.
What would be the point of China giving up on its demands for the 1 country 2 system in favor of something half-baked like what George Yeo is proposing? Once they lock in to this commonwealth thing, it would yet add more unnecessary obstacles to what is otherwise a favorable trend towards peaceful reunification under the 1C2S.
Just like poker you go for the jugular when the odds are heavily stacked in your favor, not settle for small change.