I am not able to reflect on "What if Jolla never existed" as i have not been here long enough and just came to "make that n900 usable again" and jumped on the Boat just for non google android / Alien Dalvik in the beginning.

But as you are looking for a business idea anyway, i think i am competent enough to suggest abbreviations of things keeping me afloat as a steadily growing freelancer and share my special view of the market.

1. As said before, "disrupting the market" is not possible without adequat firepower -> money. So simply forget it, the train is gone by 7 years now. Do not be the next "Don Quijote".
Consequence, make no expensive PR at all, be and attract super elitists that do not mind to spend money for top notch features/experience/customization(!!).

2. Find your niche, stay true to it and slowely grow from there. (privacy, low hw/power requirements, relatively easy to maintain).
Specialise to an extreme level but bring this specialication to the broadest market possible.

3. Plan 10 years ahead wit your rough idea.
Will Smartphones even be relevant then?

Aren't we moving towards a unified device much smaller than that? I humbely "forsaw" the Apple watch 5 years before it materialized because what i ultimately want since childhood is that frickin' "Dick Tracey" meets "Star Trek Communicator" device.
The screens will disconnect from the devics again as we are moving into a world where everything around you will be a possible screen waiting for input from your personal device.
Even Apple is still years away from that and heavily struggeling to "thin out" IOS to turn the watch from early adopters notification system playground into the next killer device.

That also is my only argument on a strategic fail by Jolla apart from "imperfect Communication":
Why did it have to be a tablet...
That sice of a device will soon be a "dump screen" only. The real sustainable challenge for sailfish would have been a watch imho.

Nevertheless i totally enjoy the ride, thank you @stskeeps for being a vital part in that experince and ALL the best of luck for your new endevours!