Well, @hvelarde, first, for your specific project, it is easy to just use webpack, configure your stuff as merger into the RR, done, if thats what you want, it does not need any RR specific compiling, just merging as @thet said.
Seconds if you use just Plone 5 it is - as @thet said - not that bad, except you try to do TTW compiling. Don’t do it. The old-but-working grunt scripts are working. I used them, I fixed tem and if you use them as they are supposed to be used it works. Sure,if you want to do it /your/ way: dont expect it to work. Meanwhile in a recent 5.1 all is OK, even if its no pretty.
Third, yes, there is your PLIP, its complex, topic is difficult, and there are so many ways around and also tools. You closed it with "I'm closing this as seems to me there is no interest on addressing this issue." Which is wrong. The FWT discussed it in depth and collected some good arguments that it may need improvement. You didn’t liked it, ok, its your decision to close it instead of improvement to find a consensus.
Also, I would kindly ask you to cool down a bit in this discussion. Some of your points are valid, but they do not need this aggressive tone. Thank you.