Creating a monopoly is not impossible, but to the point of becoming a ruler through it?
No.
That seems very unlikely, for instance.
You'd want to do trade with the elves, especially the Aldemreri dominion, as they have an incredible amount of wealth and land behind them thanks to their invasion.
Doing so would mean sacrificing all hope of trading with much of Skyrim.
As well as any land the Aldemri dominion decides to invade.
And even then, you'd have to have one hell of a mind for business, being the Dragonborn doesn't exactly offer that, and gaining the actual money, advisors, influence (in the business's world) and everything else, could be both time consuming and borderline impossible.
Also, if you're anything but a high elf, then time is limited.
And there's always the threat of the Aldemreri dominion coming crashing down on skyrim.
Which is bad for business.

Also.
Gunpowder is slightly inconsequential due to magic.
Even then you'd need to have skill to both find and then make it.
The very first instances of the rifle were shocking, and came about in Portugal in the 13th century I believe.
Guns weren't widely used until 3 centuries later.
Then there training, needing troops, cost of production etc.
So...
Sorry but they also seem unlikely.