I'll try to address your points as you gave them.  I'm not a Colemak advocate, so my perspective will probably be different than the others you'll hear.

1.) Preventing issues: Considering that many people who switch to an alternative layout (not just Colemak) claim relief when they do, it's probably safe to say that a better layout than QWERTY would be a good preventative.  That said, many if not most people go their entire career without developing issues.  Odds are against developing problems if you are conscientious, use good ergonomics and don't have any physiological tendencies toward RSI issues.

2.) Better layout: No question Colemak is a better layout.  Does that really matter that much?  Only you can decide what you're comfortable with.  There at least hundreds of millions of happy QWERTY typists.  Are they all wrong?  I doubt it.  Is less effort better?  A good argument can be made for taking the stairs rather than the elevator.  Take your pick.

3.) To improve speed.  Despite some people's claims, I see no evidence that Colemak is inherently faster.  Perhaps given everything else equal, but things are never really equal.  Talent and practice makes speed.  Colemak and QWERTY are not a Ferrari and a Yugo.

4.) QWERTY is the standard:  This is why I gave up learning Colemak.  I'd learned carPalX's optimized layout and forgotten how to type QWERTY.  It was very uncomfortable and ended up being prohibitive to performing my job functions adequately, where I needed to be able to work at anyone's computer.  I faked it pretty well but my boss could tell I was having issues typing on his machine.  I went back to QWERTY, which took quite some time, then decided to try Colemak since it was closer to QWERTY.  I could tell right away that it wasn't close enough.  I went back to QWERTY and eventually designed my own layout which is much closer to it.

4.1) Marketability: as you can see from my job requirements, it makes a difference.  If you were just a programmer or writer who's not expected to use other people's computers, then nobody even needs to know, except perhaps the IT guy who supports your machine.  If you're a Windows guy, it's a bit more difficult to switch layouts, but Mac and Linux make it a breeze, so it's no problem there.  If you decide to go with Colemak, be ok with having to look at the keyboard when typing QWERTY or be ok with practicing it frequently.  You *can* learn to do both, but it's hard and needs a lot of practice at first.  I would maintain QWERTY practice while learning Colemak.  It'll make learning Colemak longer, but you'll be better off.

5.) You're entirely correct, as long as you don't have a predisposition for injury, you can attain all of your goals on QWERTY with some diligence.  It's up to you whether you're curious enough to spend the time on Colemak or anything else.  It sucks doing it then deciding it's not worth it later, but there are loads of happy Colemak users who never want to go back.

Cheers.

Either you think you can or you think you can't, you're right. Your mind will automatically find the unshakable facts to prove for your reason.

After converting successfully, I still think Colemak is not for everyone except a very few hardcore experimenters that occupy less than 1% of the population. These experimenters tend to live according to their own rules and prefer doing things by their own way.

From my point of view, the benefits of switching are plenty, the desire to get rid of Qwerty is imminent, but the fears of not belonging to the masses are even stronger for some people.

Peer pressure is a formidable power to be reckoned with.

Tony,
I would love to do things, especially this, my own way, and it's not the peer pressure that I'm worried about. It's the inconvenience of not being able to do it the other way when I have to that concerns me.

DreymaR,
Thank you for your suggestions. Unfortunately, I don't think I can even handle just a few different keys, so I may have to drop the whole alternate keyboard thing :(

davkol,
I am definitely considering a better keyboard for when I become more stationary.
Right now, a job would be nice. I can get picky later :)

I really enjoyed using colemak and it was very apparent that my fingers were hardly moving on common words, as well as almost no SFU, but alas, I don't have the guts to really make the switch. Shall I feel more confident in the future that typing on an alternate layout isn't so bad after all, Colemak will be my first choice.

Yeah, and Dropbox is a friend in need whenever I can access the net. PKL is never far away, with Extend and all.

Even if you "can't handle different keys" I suggest trying out Extend. You will come to the dork side. It is your destiny.

DreymaR,
I checked out Extend and it looks pretty good. I'm not entirely sure how to get it working with PKL though.

pinkyache,
  It's true that everyone customizes their workstations, but usually not to the extent that it's hard to function on the average machine. The reason I'm hesitant is that for now I think it's important for me to be able to type well in qwerty at this point in my life, and ever since I learned it the first time, I've never consciously tried to improve it. Shouldn't that be the first step? Or are my concerns unwarranted?

To be honest, I'm pretty torn. Now that I'm back on QWERTY, I see how much more I have to move my fingers, and SFU disadvantage is obvious to me.
Besides for people in IT (which I may start doing part time, but I can wing that), is there any reason why not being able to type on qwerty would be a problem?

In the PKL folder there are vk_qwerty-No layouts for "passing through" the QWERTY layout you're using. That is, the AltGr mappings will be the same as those you had which may or may not suit you. I dubbed it "qwerty-No" since I've tested it on Norwegian QWERTY (ISO) keyboards, but they should work on any keyboard (although on some you may have to move the keycodes of the OEM_# keys).

You may choose between a Wide and a non-Wide version; I suspect you'll want the non-Wide for now. Then you'll need to use a pkl.ini file based on the pkl_nonAngleWide.ini file (copy-paste-rename it to pkl.ini) and set a 'layout = ' line with the name of the vk_qwerty-layout you chose.

Any trouble?