Permit permits permits. We were envisioning completing this bathroom on the cheap and on the down low. We thought the $500x2 for the skylights was the big spendy part. The plumbing looked really easy and I had a handle on the effort required. It came down to an inch. The drain pipe that went exactly where I needed it was 2 inches. The "soil pipe" which translates into the pipe for the toilet has a minimum diameter of 3 inches. This evil inch turns an easy and fun home project into a major retrofit that requires experienced plumbers. They'll be tapping into the 4" cast iron pipe that goes up to the roof and down to the municipal sewer system. This thing weighs enough that it can handily kill you of it falls, nevermind the destruction to the roof and walls involved if things go wrong. So I declare defeat and call in the experts. Experienced plumbers cost money and now we're shifting into a significant renovation. Originally, I talled up a less than $5000 cost which would be accurate if I could have tapped into that 2" pipe. Now it's looking like double that... if we're lucky. So now it's enough money that we can't (or won't) risk the quick & dirty non-permitted approach. There are other risks as well, such as insurance issues and resale... although several experienced realtors say it's more common than not to build lots of things without permits.
The next chasm to cross is the ceiling height. I believe all can be built to code with exception of that dimension. The skylights resolve the problem functionally but may not pass code because the lower roof joists fall below the height minimum. All of this is along the low side of a slanted ceiling/roof. Unless you must skulk along the low side, it's really not an issue. So we're talking to the city to see if our skylight approach is adequate. I think we're OK in the spirit of the code in making a nice livable & safe space but we're not OK if you're taking a strict conservative lowest point measurement. I think it comes down to the specific inspector. Supposing we fail to meet code, we then enter the world of ...
The dormer. If we cross this chasm we resolve all of our problems and could bang out the lower wall so instead of a 3x9 hallway of a bathroom, it would be a 7or8x9 luxurious bathroom. More permits, more professional work, a set of 4 windows, etc. etc. We'd do all the finish work but we're now into an entirely different price point. The shower would become a tub which is great.
We will see. We may be poor soon.