With your prospective timeframe, you'd want to be mindful of out of pocket expenses. Option 3 sounds really nice to me, as it is most likely to be easier to do yourself and for a reasonable outlay if you do the work yourself or with "cheap help" via out of work contractors via Craigslist.
In my experience, what gets tricky is integrating the added bath into the existing plumbing. Plumbing has a way of making a simple project more complex since the water, etc needs to go from where you'd like into the existing sewer main. The other potential pain is that the new lines might need independent venting from what's around them. And this sometimes means running a 2" PVC all the way up through your roof from the 1st floor .... yep that is fun! Otherwise, it's likely just basic carpentry and electrical.
For your new plumbing, there's this great PEX stuff. It's so much easier to work with than copper.
Good luck, Nick!