Absolutely. I agree with this because I have some projects where there will be common scenes to each individual animation. My workaround is to create a "common scenes" animation which I can duplicate and then delete the scenes which are not required and use that as the base for the new animation. Much better to be able to merge videos together.
Although I like this idea, it seems to me to start to introduce "Simplicity Creep" (like "Scope Creep".) It'd be nice if you had something that's all things to all users. However, it's already on the market and the learning curve is insane - it's called "Creative Cloud."
Great Idea. A work around for now would be to use a video edit program (i use Magix Movie Edit Pro) and import your doodly videos to combine them and save as a finished video. I am already using doodly to create segements in larger videos I create.