Consider a 25 watt F32T8 lamp. If I'm not mistaken, it is around 105 volts by 0.25A. (I know the standard F32T8 is 137 volts by 0.25A, and I assume the energy saver lamp is the same current.) The arc voltage is close to the 100 volts of an F40T12.

Now consider a residential F40T12 ballast which runs those lamps at 25 watts. Such a ballast would presumably have a lamp current of around 0.25A.

Does anyone suppose that, if you can get around the higher ignition voltage, a 25 watt F40T12 ballast would be a perfect match, both lamp and ballast-wise, for a 25 watt F32T8 lamp? Anyone have the parts on hand to give it a try?

One problem could be with the reignition voltage after current zero-cross on magnetic ballasts (there the arc disappear and has to be reignited in the start of the next half-cycle). But this is just my thinking about all hypothetical problems, I have no real knowledge, so you should try...
But otherwise once it works, the ballast, as well as the lamp shall not "complain": It sees the same voltage as the rated F40, the lamp sees the rated 0.25A, so no overloading on either side.

some ballasts are fussy enough on f40's
i guess it wont hurt to try.overdriving t8's does not seem to hurt them.have some running on cold weather/outdoor t12 ballasts 5 years now.have access to free tubes from damaged cases so i dont care if we shorten the life a bit.ballasts dont get any hotter than normal.i even run them in those crappy liteway/loa shoplights.
they start a bit rough and noisy but dont overheat.shop basement was full of those.about half died in the last few years.none had t8's though.if i get any 25w t8 i will try and report back.the place i get the freebies from uses ge f32t8/spx50.they dont get much else.