Help! I need advice on setting up large training initiatives.

Summary

I have two departments that have many repeating, required safety training courses. Some are annual, some are every three years, some are every 5 years.

Content

We are in the process of moving all training into the LMS. Previously each department  got training from various vendors and it was not tracked centrally.

One department is in year two of the LMS process. The first year wasn't bad because the most of the training was assigned to all with the exception of some outside certifications.  Year two has been a challenge because people's past completions and varied time of when renewals are coming up.  I attempted to set them up in Learning Plans using dynamic groups to assign.  But the problems just keep coming. Two big problems are: