Thank you for a very helpful post!
I think another important point is not to go all in with the corporate brand in guidelines like these. Guidelines for marketing (or worse, ppts) are inadequate for interactive learning, they're simply not designed with learning in mind, but rather marketing which is a completely different beast. I would put this additional tip at the top:
"- Don’t be too strict. Remember to leave a bit of wiggle room for creativity and originality."
Emotion is a huge part of learning, and the interface of a course is one of the most important aspects of creating the mood of a course. Messing about with guidelines that are too strict really is really getting ahead of the interface design of the learning material.
For example positive emotional states have been shown impact on learning outcomes, and using a company brand that is meant to convey something impressive, complex or even awe-inspiring will inevitably put the learner in a submissive state towards the course ("Oh, this looks complicated...").
So make sure that guidelines are created with care and consideration for the design of courses, because let's face it - the point of creating e-learning isn't to market your brand to your employees.