Reggie Rat has alfalfa meal which isn't appropriate for rats.It would be an excellent mouse food,but for rats it just isn't suitable.Instead,you could find a more appropriate seed mix to order off of Rat Rations and then add the Science Selective rat pellets.
You could even go from one seed mix to using more mixes,or adding in different seeds along with nuts and other healthy foods as you've mentioned
Variety is key,and they way you plan to do it except for just using a different mix instead of Reggie Rat will be perfect!