I use six 4 foot 6500k T8 fluorescent lamps over this 7’ Ficus Benjamina. Though, it’s also in a south window that gets direct sun.

The lights I’ve added are enough just for the very top but don’t penetrate the foliage much at all.

Anything shy of this isn’t going to give your tree enough usable light. And I wouldn’t just shine a lamp on a different part every few days. You want the whole plant getting light.

I'm really not sure there's a solution for this that will be aesthetically pleasing (which I assume you'd want for a house plant on display).

No grow light that I am familiar with will provide sufficient light for foliage near the top AND bottom of a six foot tall plant. The way light intensity is reduced as distance increases makes it a virtual impossibility.

You could choose a high powered grow light (a high intensity discharge light - probably a metal halide), which might get some light all the way down to the bottom of the plant, but it will be powerful enough that the top of the plant will probably be under stress from too much light and heat.

Also, a metal halide light will flood whatever room you have your plant in with light. They are very powerful lights, and would not be my first choice for lighting an indoor living area. I have a mid range metal halide (315 watts) in an enclosure in the main room of my apartment (to keep most of the light in - I don't particularly care about displaying what I'm growing), and the openings on the top of the enclosure (for ventilation) still let enough light out to light the entire main room of my apartment (400 square feet).

Another option would be for you to use CFL bulbs (the spiral-shaped fluorescent light bulbs that work in normal lamps), at least 23 watts each (the "100 watt equivalent" ones) with the movable "clamp lights". You can either hang these or clamp them to things, positioning them above your tree and also on the sides - however many are necessary to provide light for your entire tree. It will work, but it will look horrible.

Or, you could get a fluorescent fixture like Dave uses, hang it directly above your tree (literally - no more than a few inches above the top leaves) and just accept that your tree is going to drop all of the lower leaves due to lack of light. You will end up with a bare trunk, and leaves on maybe the top foot or so. Maybe the top two feet.

I really don't think there are any ways to light a plant that size with artificial light that will be aesthetically pleasing, and that won't create so much light that people won't want to be in the same room with it. Sorry. Most plants are not designed for the sort of living space you have, and providing artificial light for a plant that size is especially challenging.