Seedvault is pretty cool (I know you want to replace it one day but thanks for keeping it)
It would be really useful to have a shortcut though, as it is pretty hidden away.
When placing a settings widget on the home screen, all you can do is use "system" afaik, which would be a workaround. Having a normal GUI app entry for the seedvault page would also be a nice option.
The integration in the setting may be wanted, but I dont think it is very accessible.