I'm unsure if I understand this as I read it. I imagine internal apps as in-house iOS apps that can be uploaded. If you're having issues with installing the apps, that sounds like an issue more than a feature request.

If when you say internal apps, you mean in-house iOS apps, you can indeed push all at once. On the apps page, use the search bar to enter "in-house ios" and it will list all apps as such. Then, select all with the check box on the left and click on edit scope. In the dialog box you can choose which device group to scope them to.

I hope this helped, unless I misunderstood.

I found the internal apps you are talking about now and understand what you mean entirely. I agree. In my opinion they also should have been called system apps instead of internal apps, but oh well.

For anyone that comes across this, here is a reference:

When on a device page, there is a tab for Internal Apps. Each app has an individual reinstall button, but there is no reinstall all command or button on the page.