There aren't that many people in the world who write bootloader code daily for a living, an even smaller subset of those would ever have done one entirely from scratch (vs. just board-porting U-Boot), and even of those, the likelihood of someone having done a secureboot capable one wouldn't be high. Assuming you have such a person as a thesis advisor is a huge stretch ...
That said though, a thesis is (or should be) a learning exercise. Even a complete fail (to achieve the "initial" objective) can make a great thesis if new knowledge - even negative proofs, "this isn't possible because ..." - come out of it. It's just my opinion maybe, but a graduate should never be taught "fake it till you make it"; rather, describe and document failures thoroughly, explain the observations, highlight and justify the parts that work or are breakthroughs. That can make a much better readable and much more useful thesis than one that skims over one-time lucky else nonreproducible results and delivers uncommented sources that fail to compile for anyone but the original author. In that sense, I would argue that a good thesis advisor will focus on the scientific process, documentary evidence, clarity of experimental setups and tests/checks/benchmarks performed, not whether the outcome would be "great enough" to pitch as a founder to VCs.