What t5 bulb brand and wattage do you use?
6k per cubic ft seems great.
Because most lighting is chosen based on price, efficiency, and grow setup.
Running HPS usually requires extraction fans to be ran at a certain level, running LED allows extraction fans to be ran much slower, thus saving on wattage.
Thats just one example, but you can see how everything begins to link in...
Running all sorts of lights would likely be the furthest away from efficiency you could get.
Also to answer you question of would there be a benefit to running diff light sources. - I doubt there would be any significant benefit, but there are significant benefits to not catering to multiple light sources(one being massive headache of light positioning, etc)