All I can say is. give it time. Addons are still VERY new and they are actively being worked on by Mojang to allow more and more things. Soon, we'll have everything that can possibly be added from Java/PC Edition and more. If we can get more of the Java/PC modders to work on addons, it would help. As stated before, don't expect everything in Java to make it's way into MCPE/Win10. Some things just aren't possible, whether it be caused by a java bug (BUDs and quasi-connectivity) or the simple limitation of our version having to run on smartphones.
The Meaning of Life, the Universe, and Everything.
I've heard rumours that there is an official converter between Java edition and Bedrock edition in the works. This is not confirmed yet, but people have found files that hint at it going to be a thing.
I've also had people tell me of an existing tool. I'm gonna look it up and test it first, but if it works, it'll be possible to convert Java edition savefiles to MCPE savefiles. As zefxyde said, not everthing will make it across (some blocks are not compatible), but basic stone and grass should not be a problem.