Well, fuel cells are clearly superior to ICEs, and the only thing really keeping them in check are fluff reasons. Even their supposedly lower operational range (unlikely to come up often at the playing table) is to some extent a myth -- fuel cell engines are actually more fuel efficient than internal combustion, they just carry a smaller fuel supply with them by default.
(Using the factors given by the TacOps fractional accounting rules for simplicity's sake, fuel cell engines weigh 60% of their ICE equivalent while getting 75% of their range...and the same ratio holds true for their fuel tanks, where investing 10% of the engine's weight adds its base range again. Not using fractional accounting complicates this somewhat with rounding errors, but the basic principle still holds.)
So, really, if the fluff wasn't holding them back, there'd be no reason not to upgrade every single ICE-powered vehicle in existence to fuel cells straight away.