If it works, or even if it only partly works, this hydrogen + boron reaction may not be the only possible one. It's possible that the idea itself could spawn a new way of looking at the problem. Ideally you could do something with the helium by-product, and fuse to larger elements.
Fusing things heavier than hydrogen takes increasingly extreme conditions. The reason we typically try for helium fusion is because the proton-proton chain's initial reaction is really, really, REALLY hard to make happen, so difficult we can't even measure the reaction's cross section experimentally. Fusing heavier elements involves overcoming increasingly large Coulomb barriers with processes that are highly temperature dependent (we're talking about processes with exponents like T
40) and thus tend to be rather unstable when you don't have an entire star pressing down on the fusion region to keep things from getting out of hand.
It would be nice to be able to just decide we want some more [element] and order up a fusion reactor to make some, but not only would it be a rather slow process to get meaningful amounts of said material, you also have to hope that most or all the processes necessary in said hypothetical super-reactor don't go spewing neutrons all over the place, as that can either contaminate everything you make with radioactive isotopes or outright alter the materials you're trying to fuse and thus reducing output.
And of course instead of the usual suggestion of a reactor fusing helium that works "like the inside of the Sun", you'd need a reactor capable of simulating the inside of not just the Sun, but a star much, much larger than the Sun and with correspondingly more ridiculous pressures, temperatures, and densities.