You can get around the tritium problem with boron-proton fusion. Also gets around the inefficiency of converting to heat / turbines. Obviously not any closer to production (and probably further) than tritium fusion, though. https://hb11.energy/how-it-works/
It's been done by firing lasers at a HB pellet, so I assume you mean not possible to be done commercially? And why would you have to reflect gamma rays?
Obviously you can fuse about anything by accelerating nuclei at each other fast enough. If it takes more energy to do it than you can get back, it is of purely academic interest. Firing lasers comes up many orders of magnitude short.
Another alternative is magnetic confinement, but radiative loss goes up with the 4th power of temperature, so would be 10000 times as much as for a D-T plasma, IIUC.
