I like the idea of the Colfax line joining the light rail line to go to DUS. I think its important to have Aurora involved in the Colfax line because the natural eastern anchor is Fitz. Also, how would the interface of the Colfax line and the I-225 line work? Maybe it goes north on peoria to peoria station and there is a Fitz station on the west side of the campus on peoria? Maybe it goes down colfax all the way to the 225 line and trains continue on along the south corridor? I think its important to think about how this connection will work.
A hard area to service is Highlands, because there are so many barriers between DUS and Highlands (RR Tracks, the River, I-25). Maybe the way to do it is from a Colfax line that turns north onto Federal. Heading west, you could have 2 termini for the colfax trains, DUS vs CPV and Highlands via North Federal.
I don't really know what a downtown spine train adds that isn't already being done with the Mall Ride and new downtown circulator.
Cherry Creek Route seems good.
As for financing, I would look at a land value tax (different than property tax..
http://en.wikipedia.org/wiki/Land_value_tax