1/8" Spindle - brainstorming

I had a good idea that I don't quite know how to pull off. My mill
will handle a 1" end mill. I was thinking that if I could fabricate
a spindle with a 1" OD and a shaft with a 1/8" collet I could chuck
it in the end mill holder. You could power it through a cog belt
from a router motor mounted on the mill's spindle. This would give
me the ability to mount a high speed spindle for small tools without
loosing my x/y position. Height could be handled through tool length
compensation. To the mill its just a tool change. Probably not
continuous duty but OK for my playing.

Some problems are:
* Where can I find a spindle with a collet mount. I like this one
but its OD is too large: http://www.use-enco.com/pdfs/170.PDF
* Can you fit enough shaft and bearings in the 1" OD to be rigid
enough to use? I think the taig spindle is almost 2".

Any thoughts?

Roger