Feature request | Better support for custom widget classes

Hi there

Thanks for a great plugin it rocks!!
We are using this plugin on a lot of projects but we often see ourselves building additional JS stuff to make it even easier to be a site builder.

We often add our custom “class select” input for the class selecter because the user does not know which classes to use/insert.
Here is an example on how we add our custom select.
https://s3.postimg.org/vgbfxd0wj/Screen_Shot_2016_08_18_at_18_41_15.png

Would it be possible to use a filter/action instead of adding JS layer on the top?

https://ww.wp.xz.cn/plugins/siteorigin-panels/