User blog comment:Dragonjet/KC3改/@comment-49.145.53.68-20150831035749/@comment-26091666-20150831205418

If you're implying as a standalone viewer a similar suggestion was made by another user as well. To be honest, that idea will have lots of hurdles for implementation due to the very fact that it will become more or less OS/platform specific.

KC3 Kai is now enjoyed by users from both Macs and Linux users as well due to the fact that it only depends on Google Chrome whereas KCV can only be enjoyed by Windows users.

To implement the ability run a flash player or even better the ability to act as a mini-browser as what KCV does will not only make it platform specific but:
 * it adds extra weight to the viewer, so the viewer becomes big.
 * it adds several new issues ranging from as simple/trivial as
 * which browser (engine) to throw in
 * compatibility issues
 * maintainability issues
 * other issues such as wrapping around the largely proprietary Adobe Flash engine.

Another key benefit with KCV is that the overall viewer can somewhat be lightweight as it is built around .NET framework which inherently includes the parts for a browser along with direct access to a very well maintained version of flash player by Adobe. However the point being that again it will be very OS/platform specific and not to mention the extra burden the developers must face.

TL;DR it is best to leave it as an extension because developing and maintaining extensions is far simpler than developing and maintaining standalone programs.