Two systems in one country practice in Hong Kong is projected as

The main reason why Taiwan doesn't like this two-system-in-one-couny poposal is that the same practice that has been applied in Hong Kong is widely viewed as an unsuccessful practice.  Some people in Hong Kong, especially those young people belives that their freedom and rights are squeezed.  They took their claims on street few times but the attempts didn't return the results they wanted.  So there are some bitter resentment toward this practice in Hong Kong today.  While attemping to sell the same idea to Taiwan, it is not hard to understand why Taiwan people don't like it.  So mainland side sould take this into consideration and offer taiwan with something better, gurrantted and durable.  People can't just blame Taiwan side without switch the position and view the whole situation from the opsite direction.

Still, some people and interlectuals in Taiwan holding positive view on this two systems in one country idea and willing to start the conversation at least.  If mainland side can provide some more details and incentives on this idea with bit of military pressure, that could help to get the talk going.