This is a great start. Granted this appears to be a single speed generic gear box, it is still a great learning step when it comes to designing gear boxes.
To Michael's point, pockets in the plates do have advantages, but there is cost associated with them.
The two most obvious advantages are: Weight saving, and they look cool.
That's about it.
Here are some of the costs associated with them: Extra design time, extra machine time, not as robust as flat plates (this point is arguable), time to clean up and de-burr.
Here is a really excellent
YouTube Channel put up by 973. Adam has invested a lot of time in creating content about robot design. This includes a couple videos on transmission design and even on pocketing. One excellent point he makes is to NOT invest time into pocketing until you are absolutely certain your design is right. Trust me on this, it is excellent advice!
All that said, I also want to acknowledge your work. That trans looks really nice!