Keep default widgets on theme change

Hi guys,

I'm very happy with your New Blog Templates plugin, works like a charm with default theme.

I'm wondering if there a way to keep default widgets if users in my multisite change the theme?

I found this thread: https://premium.wpmudev.org/forums/topic/assigning-default-sidebar-widgets about hardcoding widgets, however this is not want I want - I must give my users option to delete the default widgets if they want to do so (hardcoding want give this option).

I was hoping if I go through all themes on my default blog template and add widgets to all of them it will stay like it, but once the theme is changed all widgets are gone.

So basically what I'm looking for is a way to assign different (or the same) widgets to different themes, so when user changes the theme the widgets will stay there. It is a real pain in the .... because users without technical knowledge keep complaining about it all the time.

Thanks
Tom