Android ships a feature called bootchart which you can use to prove that most of the time your phone spends booting.. it is actually far from bottlenecked on storage or compute - bugs to be fixed; not worked around with even more complexity. Heck, some phones do not even stop playing their vendors fancy animated logo when they are finished before the animation is.

Does it take into consideration thermal and power? Doing too much too quickly can be bad for both, so sometimes it's worthwhile to go slower.