Interesting
David.
I recall about 4-5 years ago posting a similar drawing allowing for a fourth access point from Elmwood Drive too, but utilizing a standard diamond interchange rather than a reduced radius roundabout.
Not being a traffic engineer, I would be worried that a reduced radius roundabout would cause increased traffic congestion as lower speeds would be needed to enter into the roundabout than are necessary with the current traffic circle. I don't think commuters would be very pleased.
This isn't to say that the current traffic circle is perfect, but it does work reasonably well most of the time, mostly because the large radius gives drivers a few extra seconds to plan lane changing manoeuvres.
The biggest pet peeve I have with the current situation is the westbound on ramp from Lewisville/Paul onto Highway 11/15 just before it merges with the traffic circle. This situation is just plain dangerous and I tend to avoid it by simply continuing along Lewisville until I reach the signalized intersection at Lewisville/Botsford with Wheeler Blvd. Getting onto the 11/15 westbound here is much less dangerous.
I think this problem could easily be solved simply by extending the westbound on ramp further, along the outer circumference of the traffic circle, and making it an additional exit lane from the traffic circle onto Wheeler Blvd. By doing so, you eliminate any concerns with merging with high velocity traffic in a blind spot coming from Veterans Highway.