The major thing you need to be aware of with using different eligibility for deferrals and safe harbor match, is that you no longer get your free pass for top heavy. If the plan ever becomes top heavy, you will be subject to the top heavy minimum, even if the only other employer contribution for the year is the safe harbor match.
Other than that, there is no problem with having different eligibility requirements for deferral and match. For the ADP test, the employees who have not completed 1 year of service are disaggregated as otherwise excludable, and as long as they are all NHCE that group does not need to be tested. For the other group they satisfy the ADP/ACP test by way of the safe harbor match.