No. You cannot. Because the application dashboards are not independent, instead they are dependent on their parent widget, which was the panel. Since it's removed, your application launcher or dashboard is also removed.
However, if you really want to get rid of the panel, you can do this instead.
- Remove the panel.
- Add the required widgets to the desktop. You can do so, because these widgets can be added on desktop too!
- Once added, press and hold the click to get the settings/preference window of the widget. There you can set a keyboard shortcut like Alt-F1
You should be able to use the widget now. Repeat the process for all the other widgets you use.
There will be one problem still and that is the icons of these widgets will stay on the desktop. But you can resize them and arrange them so that they look like native to your setup.
Hope that helps
Following user requirement, it seems recently a dock is appearing for KDE named Latte-Dock. The deb package provided in the github repository needs QT 5.7, which is difficult to grab in Kubuntu 16.04. But fortunately some people from mint forum figured out that it can be built using QT 5.6 easily. I tested it and indeed it is. Follow the instruction on the forum post.
Here is a screenshot of running only a dock in KDE5.