Unless I am missing something, this is a basic all-glass railing assembly. A continuous rail shoe fitting is the standard way to support these. No need for a whole foot of glass to be recessed. Depending on your local code, you may need an engineer to sign off on this. 

Thanks, Rusty.

The issue is first that the shoe will not be exposed sitting on top of the kneewall cap.  Only glass will show above the cap.  Second, I probably should make more clear that when I say "bottom-lit", I mean lit "through" the bottom of the glass pane, not just a flood light placed alongside the bottom of the pane.  Something like this:

     |

     |         Glass pane

     |

----|----    T/kneewall cap

|    |   |     What supports the btm. of this pane while simultaneously allowing (most of) the

|        |                light to enter through the btm. of this pane?

|  O   |     Tube light

|-------|

Rusty is on the right track.

Continuous T5 fluorescent tube lighting may not be the way to go. A series of point light sources may be more effective. Keep in mind that point light sources often have a parabolic  distribution pattern- in theory, you could align the distributed light to appear continuous but also have space in between for extra support. Something like the following:

- - - - -(top of knee wall) - - - - -

| (wide dimension of glass)  |
|______________________|                          Bottom edge of glass in elevation

  V  .   V   .   V   .   V   .   V   .   V

Where " V " is the distribution pattern of point lighting and  " . "  is a potential support location.

You would essentially align the tips of the V's to look like VVVVVVVV. This would give you a continuously illuminated edge. Due to the supports at the bottom edge, you should try to conceal the shadowed region (where there is no light) beneath the knee wall.

You could also approach this like cove lighting- stagger tubes on both sides of the edge at the bottom to achieve a continuous effect. You may be able to get vertical supports running continuously at the bottom in that case.

    |____|                                              Section taken perpendicular to wide dimension of glass

O     X      O                                          X = support, O = tube

Have you tested to make sure this idea will work? I've used the detail of supporting the glass from a conventional channel frame and offsetting the light source in an adjacent pocket. I cannot see how what you are proposing would be radically different.

Not to be totally unhelpful, if you do want to leave the bottom edge of the glass exposed to position the light source directly underneath, you could use point supports or spider clamps along the edges of the glass. You would then need to devise a way to access the light in the kneewall, but that's another issue.

I think I am saying the pretty much the same thing TokenAE is, but I would recommend limiting the number of point supports to use a tube fixture fluorescent or strip LED. Too many light sources will not produce the light wash effect you seem to be going for.
 

Thanks everybody. I'm going to run a few ideas by the project members.  I haven't tested it.  Just curious, won and done, why wouldn't multiple light sources give a light wash effect?  Only a small gap, or slit, in the kneewall cap will allow the light to be released up the pane, no matter how many light sources are provided inside the wall.

some heavy duty clear acrylic setting blocks might work well.  i'd recommend an LED tape light, if you can find one with enough power.  WAC lighting has a nice product I believe.

providing access to the lighting for changing lamps etc, without a big ugly access panel is always the trickiest par.  good luck!

I think you should buy one of these instead and call it a day.

A translucent acrylic would work better to carry the light through the sheet and omit via the faces, not the edge.  Edge lighting glass typically doesn't illuminate the panel even if there's an opaque/translucent  pvb layer.

Alternatively, you might try an electroluminscent film embedded within the glass.  http://www.luminousfilm.com/

Just curious, won and done, why wouldn't multiple light sources give a light wash effect?

Trust me, I've done a few of these. If you use multiple sources, it will not produce an even  and consistent wash of light. There will be hot spots immediately next to the source. Given the area you want to wash is relatively small, I think an LED strip will work fine. If you are not getting the light output you need, you may want to go with a fluorescent, but the quality of the light will be different.

My advice: invest in a mock-up.

On thing you should keep in mind in detailing this is the heat of the bulb and where does that heat go.  You don't want to be burning down a building cause you forgot to forget about all the the trapped heat.  I would suggest  led rope lighting but the manufacturer would most likely say you should not conceal the rope lighting in a tight space due to overheating.  

lots of luck....You need to talk to the "Lighting Gods".