Note that which "person" you write in is orthogonal to---not necessarily tied to---whose POV you write from. For example, if you write in the third person I strongly recommend that you pick one character's "head" to "inhabit" for each scene (and preferably no more than a handful in each story), and stick to his or her point-of-view for the duration of that scene, describing things and events as he or she perceives them ...

essentially using his or her perception as the lens through which you focus the reader's perception, in contrast to first person where the character's perception functions as the camera. This is only slightly less limiting than writing in the first person (since you're still writing from a character's point of view), but it's much less jarring to switch whose POV you're writing from (so long as you don't try to switch mid-scene, and clearly establish whose POV we're in at the beginning of every scene).

From a readers point of view: I always get impatient whenever the view switches to someone besides the MC, especially if the other character is a bad guy. It drove me crazy during Red Wall, but maybe that's just me.

If you did switch POV, my recommendation would be to create another likable character, with his/her own sub-plot that runs through out the book(s), so it's not just about gaining information. (This may already be what your thinking.)

Even in third person you can still get inside people's head, but if you think it would make a big difference and add a lot to the character to do it in first person, I say go for it!

I don't really think you should switch from first to third mid series. I think I would get attached to the first person and be sad to see it go.

Writing the whole series in first person could be fine, if you can manage to effectively tell an epic fantasy story that way.

There is also an unconventional method that some writers use: Writing the main protagonist in first person, and all the other characters in third person.

My thought was more in consideration of the entire series. So, for example, if I write books 1 and 2 entirely in MC's 1st person POV, would it be acceptable to write the remainder of the series in 3rd person, which would include MC?

The thinking behind 1st person was the use of personal pronouns such as I and me. Having the MC talk in that fashion, instead of using their name in 3rd person, to me anyway, gives the chance to delve more deeply into their thoughts and make their experiences more personal.

There's a distinct difference between saying so-and-so is horrified and I'm horrified, especially if the character has inner turmoil you want to stress. At least that's how I view it.

That was my fear: being able to create a series with a huge scope while being restricted to one person's head for the entire journey. That seems almost impossible.

There is also an unconventional method that some writers use: Writing the main protagonist in first person, and all the other characters in third person.

You could have some parts told as letters to your main character, or some such. (Writing from only a single POV, possibly plus documents and such he or she reads, would be good practice if nothing else.)

personally, having seen third-person limited done so well

An excellent idea in moderation. But with the vast amounts of information I'd have to impart, it would become redundant after awhile.

Could you give any examples?

That was the question I wanted answered most. However, would switching to 3rd person but still including the MC from that new POV be all right?

You could do it. It's not so much that I would miss the MC, but I feel the transition could potentially disrupt the flow between books because the styles are so different, and could therefore come as a shock to readers.

Of course, you could overcome this by effective writing. Maybe you've reached the climax and resolution of the MC's inner turmoil, and a new, broader plot is escalating. This might make the first books seem like a prequel, but it wouldn't feel so abrupt. There are probably other things you can think of to get around this, having written a ton more than me.

Before you get started, you might try reading a couple 3rd person limited books that have good man-vs-himself conflict and try to learn how feasible that is to write.

Tarin: I'd say don't write one or two books in first and then the rest in third. It would feel odd to me, personally. Pick one or two and stick with it.

Switching to other people's heads could be a problem.

However...if the story is kept VERY MUCH focused on your MC, I would be inclined to forgive you since variety IS the spice of life.