Drive Switching CC Buck Converter with PWM?

I have an unused DB917 buck converter that’s been in my parts box for nearly 10 years.

Can I use a Nanjg 105C and replace the 7135’s with an FET to drive the buck converter from 2 x CR123 primaries for a more efficient driver with modes?

I did something similar long ago using a CR123 +Fenix L2P head, and a NiteIze IQ tailswitch. Biggest drawback was the visible PWM, but otherwise worked OK.

Of course the L2P used a boost converter, but the setup worked well enough to make me think I might drive the buck converter with PWM.

I’m really just wanting a an efficient (%80 or better), well-regulated 1-amp driver that I can program with custom firmware and run on 2 x CR123’s as well as 1 x 4.2V lion. Oh, and without the visible PWM…

Any thoughts would be most welcome.

Thanks,
JW