How hard is to do something like this

I wanted to ask for your opinion - how hard do you think is to do something like this :
is it wort to do in Unreal or better stick to three.js and javascript overall?
How fast will it work?

The hard part is to achieve a light weight. The example download the content very fast. With ue4 you have to download the engine and content.

Thanks for your reply.
Looks like it is better to stick to javascript for this one.