The real problem with SaaS is that offline use is still sketchy and users really do need that functionality. I'm working on an "Offline First" app now, but it's not really offline "first" because "App Cache Sucks" and "Service Workers" are not fully implemented yet.
For example, in my test with Safari, Chrome, and Firefox, on Mac OS 10.11 my app using "App Cache" for offline use requires the user to click on a page that loads a resource before it can be used offline, even after the "cache manifest" has been updated and all the files downloaded. And Safari doesn't support "Service Workers".
Beyond that, Safari doesn't really use the updated files when you update the cache manifest. I have had to use the "Empty Cache" link under the "Develop" menu to insure that when testing.
So, if a user empties their cache for whatever reason they break the app for offline use so that's yet another issue that presents a problem.
That said, Service Workers do look promising and the apps I'm working on are blazing fast and work great offline when everything is working as designed.
The age old problem with desktop apps is developing for multiple platforms. You either spend the time and money to do that or you lose out on the market you ignore.
There is another promising viable option that's been mostly overlooked...
That's shipping your app on a Raspberry Pi and integrating that into the user's office. They can use it as a stand alone desktop PC or as app server connected to their LAN, and/or the internet. This approach is getting a lot easier, but since it's not being done yet it will require some hand holding for most end users to integrate into their LAN or set it up as an internet server.
To me, that is really the most interesting option when looking forward.