At first blush, it sounds like a great idea, but only one person has attempted to quantify what it really would require in terms of zoning.
Bernadette Kelly of MOA describes "block sensitive height limits" as a solution. Similar to how the context sensitive front setback is calculated, it would regulate building heights based on the current status of what's on the ground. She cites an English "right to light" law that derives from the Druid civilization. To paraphrase: "if a structure has had access to the sun for at least 20 years, it is illegal to ever block the sun from that structure".
It does solve the problem, would satisfy most solar advocates, but it is a bit impractical to implement, and would greatly diminish your neighbor's current property rights. (Full disclosure: the author is a solar advocate, but hopes to profit from the ability to increase density in transit neighborhoods)
It's doubtful that this proposal will see the light of day in this version of the zoning code, but it's not without merit. Some neighborhoods of one story homes and large side setbacks may want to STAY neighborhoods of one story homes and large side setbacks, and there are no tools in Zoning Code draft 3 to help preserve that context. Two story homes have always been allowed everywhere in Denver, and CPD has thus far refused to change that.