[Boromir88]

Good news Form, is Tolkien did write about many of those Beorn assumptions.

Though a skin-changer and no doubt a bit of a magician, Beorn was a Man.~Letter 144

It's sad though that all we have is Tolkien's responses, not the letters that were sent to him. Personally I've always imagined someone asking why Beorn wasn't in LOTR, as Tolkien first said 'Beorn is dead' and references Gloin in Many Meetings. Tolkien who worked and worked to try and fit The Hobbit with LOTR, did not want to pull a Bombadil trick. He just decided...'you know what I'm not going to do this anymore. Beorn's not in LOTR, because he's dead. He's a man, a bear shape-shifter, a magician, and immune to weapons, but the dude was a man and he's now dead. The end.'

Hopefully you don't mind my early morning silliness, but with that aside, it does fit with what Gloin says about Grimbeorn being the 'lord of many sturdy men.' I think Tolkien took from the berskergang stories, and put his own fantasy spin on it. To my knowledge Tolkien never used the word 'berserker,' but with Beorn he was definitely referencing one common meaning of the berserker ('bear-shirt' - the berserkers who would wear bear skins to battle). Plus, berserkers were of course known to work themselves up into this battle-fury, even some were said to be immune to weapons, like Beorn at the Battle of Five Armies :

Swiftly he returned and his wrath was redoubled, so that nothing could withstand him, and no weapon seemed to bite upon him.

Surely he isn't dependant on gunpower for such varied displays.~Inziladun

Yes, and I think even his fireworks were enhanced by his magic. We meager humans, through all our gunpowder and fireworks evolution over the centuries struggle making some rather simple designs. Gandalf managed to create a mountain scene and a flying dragon with his fireworks. Gandalf and the Elves typically used magic for artistic purposes afterall.

I suspect Saruman enhanced his blasting devices with magic as well. I reference 155 again:

The basic motive for magia - quite apart from any philosophic consideration of how it would work - is immediacy: speed, reduction of labour, and reduction also to a minimum (or vanishing point) of the gap in time between the idea or desire and the result or effect.

You want something accomplished, magic's purpose is to speed it up and cut back on labor costs.