So what about the needles?
I'm not familiar with Mugo pine, only Black and White pines, so I'd look up an in-depth article about Mugo pine training, like this one, which I assume you have already seen:
bonsai4me.com/AdvTech/ATMugo%20Pines%20Indepth%20page2.html
There are posts earlier in this thread that the tree has far too long needles. I complettely agrre on that.
Sure, but of no concern, really, in this stage.
Off cource I can remove all the long needles to make the tree more estetic as of today. However all needles remaining helps to grow the trunk thicker. I do want shorter needles and I do want thicker trunk. So I see this as some sort of dilemma, ok looking now or even better in the future?
Growth is more important at this stage, so, you're right. Do not remove the needles. It's something for the future.