Andrew referred to Handel’s Water Music. Several temperaments can accommodate three keys (in this case, D, F & G) comfortably.7) Temperament need not necessarily be "fixed", either: JS Bach could reportedly retune a harpsichord in less than a minute; there are other reports of harpsichords being tuned every six months, whether they needed it or no. The harpsichord’s role in ensemble is more percussive than harmonic. Those who have performed on balconies with real church organs will have noticed a significant difference when returning to a stage with a small, portable chamber organ, mainly because of its artificially-central position, leading to a poorly-supported 8) assumption that unrestricted "voice" instruments should try to play in a temperament that compromises a desirable 31 notes per octave into a manageable 12 (or 14, with two split keys) 9). When a chamber organ is placed outside the ensemble, emulating its normal distance in an organ loft (if not its height) and played with tonality-aware voicing, it allows space for the temperament to "breathe" with an undisturbed, purely-tuned ensemble. If composers wanted their music to sound like an organ, they would write it for solo organ.
Since we seem unaffected by the Trade Descriptions Act, and some apparently consider the word "historic" to be a technical inconvenience, the logical conclusion of progress through compromise - to eliminate human error - would have the score programmed into a computer (in a nice wooden cabinet) and played through veneered speakers - both of which pre-date the introduction of three and four-hole systems on trumpets, double staples on oboes, outer-scraped reeds and thin-gut-or-synthetic-cored strings. Electricity is needed for the lights anyway, so everything would be just "perfect" and could be uniformly manipulated into any temperament. The musicians would only need to mime, avoiding the horrific possibility of mistkase. It would then be cheaper to hire better-looking actors, or even robots, leaving more money for conductors; until even they are replaced by more reliable, wood-effect metronomes.
1)"Messing" is German for brass.
7)See: Claudio di Verroli: Unequal temperaments: theory and practice (2008-9) (e-book)
8)Many sources cite pure intervals as ideal and I have not yet found one insisting that violinists tune all of their open strings to a keyboard, although Quantz suggests a slight narrowing of fifths as a possibility, complaining of a fashion for tuning e strings too high. The dogmatic use of open strings by default is another issue.
9)See: HOLIER THAN THOU, Who’s in tune? and this picture