Long read: Playing Baroque and Classical

There used to be two distinct schools of playing, Baroque and modern, of which it was thought that ‘ne’er the twain shall meet’. Now, however, there seem to be bandwagons travelling constantly between the two; period-instrument groups frequently import modern players and in their turn modern orchestras invite old-music specialists. To facilitate this crossfertilisation, what compromises can be made regarding equipment and the various elements of technique?