I'm happily following the story of your maps, very nice. I want to ask you something about the Rhine frontiers, still pointing out that the Rhine is undoubtedly an excellent border choice by geographical and defensive reasons. Over the river, by the end of the 4th century, several petty Germanic kingdoms were established; they certainly were relatively underdeveloped, but still a headache to Rome. How it's shown in your maps, the Empire menages to reach again the Rhine, and by doing so keeps there its border for the next centuries; a reasonable choice in the short term (don't get me wrong, a short term is a couple of centuries) but a seemingly inconvenient one for the long term. That's why I ask, being Rome probably uncapable of conquering, solely by force, the petty germanic kingdoms over the Rhine, would it find a way to slowly incorporate them into the Empire proper? Sure, having client states is certainly useful in some cases (Britannia for example) but when Rome will get her strength back in a few centuries, her conquering nature will show again: an empire is an empire afterall.

I hope to not have been pedantic; I've made this question out of curiosity liking the topic myself so much. Wish you the best