ActionScript 3 framework / engine for building social game like FarmVille

The current architecture of the game is:

• PHP + MySql backend,
• Flash and ActionScript 3 frontend.

Major criteria for engine/framework selection are:

1. Support for isometric view.
2. Resuability : The current game development should easy the work for building similar social game of diffrent story type in future.
3. Ease of development

Already researched stuff:

1. as3isolib - for isometric rendering, but restricted only to the rendering part.
2. PushButton Engine - open source engine, component based
3. Open-space engine - But That works with Smart Fox Server only I guess.

Any other good recommendations ?

I'm not suggesting any particular engine. The choice depends on a number of factors like number of people in the team, target time period, expected number of users, budget etc. etc. But you should check this list of flash game engines. And also check this list of flash isometric engines.