Sorry, this is the electric, not levitation forum ;)

Seriously, what other solution could there be?

Here are my thoughts:

1) hire an electrician who will, no doubt, have access to a longer stepladder.

2) rent a longer ladder, assuming you know someone/have a vehicle suitable to transport it, although many rental houses offer a delivery service. I would suggest, since you are doing the friend a favour, suggest she rents a ladder and organises it to be there.

Maybe make sure her liability insurance is up to date. I would assume you are covered, provided you are not charging her money, which I assume you are not. 20' is a long way down.

Otherwise, not really your problem, ultimately.

Stilts

I don't think you will find a step ladder taller than 16'.(Remember you can't stand any higher than the 14' level on the ladder).
Your best option will probably be some scaffolding and walkboards.
I hope your friend realizes just how much this little project is worth and what it will cost.
Hiring a licensed electrician, you are probably looking at $600-$700.

Yes, finding a local rental place that has a step ladder that size is probably going to be a challenge. Maybe not though.

Scaffolding would be fine too if I can find one that would fit. The entry area is 6x8 approximately.

My other thought was a narrow scissor lift that could be brought in through the front door.

I will have to go around to the rental places and see what they have.

This is already a PITA and the work has not even started.

Maybe I can convince her that simply cutting the old fixture off and wiring in the new bronze fixture with the gold chain will look just fine.

Erm.

Well, when changing lights around at a semi-local theater, I was introduced to a truly scary invention - it was something like a 25-foot wooden stepladder. That sucker was a c*nt to move and not very pleasant to use either. However, they do exist.

If the area is only 6x8, could you just use a regular extension ladder leaning against the wall and still reach the light?

An extension ladder could be an option for sure, perhaps not quite as safe. I would recommend you work out some way of wedging it so the feet won't slip, unless it's on carpet.

You will want to attach a board across the top and cover that with soft cloth so the legs don't go through the drywall/scuff it.

Scaffolding could be an option, painter's stuff is small enough.

As for stepladders, I've seen some scary tall ones, tall enough I'm sure. You will want to double check the measurements, it'd be annoying to find you have one TOO TALL to stand up, also there's the issue of whether there's room to get it through the door.

I agree, it's growing into a big job your friend probably doesn't realise, although I would be with her on wanting to get rid of the ugly 'builder grade' fitting.

My sister-in-law, whose family is in the spec home building trade is always boasting about what great work they do and how much better their work is than the spec home builders here in BC Canada, then she drops something about how her sister buys light fittings for the houses "on sale at Canadian Tire."

Now don't get me wrong, you can sometimes get some good stuff at a good price there, but as a rule, light fittings on sale are not exactly going to be wonderful and stylish.

As I've replaced the spec fittings in my own house, I've even debated with myself the merits of taking these awful things down to the ReStore which is already filled with junky fittings that will NEVER be classics...but still, people buy them. I guess for a closet or storeroom where you just need something to get around the 'bare bulb' law, it works.