if you want good CRI go for Nichia 219C they can use 9050 CRI >92
A nichia 219 can easily provide 300 OTF lumens within specified current range and 2 hours runtime on a 3000mAh battery
http://www.nichia.co.jp/specification/products/led/NVSW219C-E.pdf
this is a sick test for the LED the manufactor rates the LED 1.8A for around 550 Lumens
your 300 Lumens goal after optics should be within the 1400mA range
there are also some CRI >95 LEDs
go for a neutral white tint around 5000K its like direct sunlight very pleasant to the eyes
http://www.nichia.co.jp/en/product/led_search.html?op=cond=application='General%20Lighting'
good light with minimal modding to achieve your goal, 2 hours at highest brightness mode
http://www.gearbest.com/led-flashlights/pp_411562.html?wid=21
has a nice driver and USB charger and 1.6A CC driver
basically you need some thermal glue and a Nichia 219C on a 16mm round board
just 3 output levels no strobe
a really nice host
you need to do a driver
and use the space within the light to add a USB charging port, would be a new mod, very nice
if you want to implement temperature control for the LED you need an Attiny25 MCU
for all those specs I really dont know in which host you build this
if you skip the rotary thing a Klarus XT11 series light may be the one
you need to reduce the current by increasing the shunt on the driver and replace the LED with a Nichia 219
on 3535 footprint you need only reflow the new LED