Hi.
I have investigated things a little.
I have found that VIA provides sources for build of image based on Yocto Dora 1.5.
So, the main task is to rebase build procedure from Yocto Dora 1.5 to Yocto Jethro 2.0.
This is quite common task and can be devided into incremental update steps: 1.5->1.6->1.7->1.8->2.0.
At my primary work I deal with maintenance of Yocto building WindRiver Linux 5.0 image, so I consider myself experienced enough for this task.
I have some questions regarding the rest of the project.
You said "I need Qt5 toolchain". What do You mean? You want to be able to run Qt5 application on the board? You want to be able to login to the board and develop Qt5 apps there?
Regarding SQLite - should board be able to host database or be client to the external database only?
Regarding Your application, how You plan to integrate it? Should it be part of the image? I will need it then. Or should it be called by the image from external filesystem?