Hello, apologies for late reply. If I understand right, you are essentially proposing using your own tweening functions. This is certainly an option, and not a bad one either! As you said, tweening the C0 of a Motor6D directly instead of a CFrameValue with an event connecting it to the target C0 might lead to slightly less resource utilization, and would also allow custom easings.
I will say, however, that using TweenService allows you to easily delay and reverse poses using the respective properties of TweenInfo. Roblox also has InterpolationThrottling (although it still annoys me that tweens themselves aren’t replicated and instead the results are!!!) which is pretty useful.