Hi,
I suppose that would work.
You might consider using aluminized mylar instead of emergency blankets -- its available from some of the hydroponic places.

The commercial solar tubes do include a gadget on the top end that is supposed to direct more light down the tube -- you might want to take a look at this at a store.

I guess you would just want to be careful not to make a big heat leak from your living space to the attic where the new fixture goes in the ceiling.

Gary