Do so at your own risk. Yes it will work as long as all components are
functional. If there is a fault, it will damage both systems. Ask yourself
why anyone would wish to combine alternators on the same battery bank at the
same time. It is self defeating.

Not really. It provides unattended backup charging if one alternator fails.
Although it certainly is theoretically possible that a failure could damage
something, I have yet to see it happen in a dual alt charging system on
commercial fishing boats which often put thousands of hours per year on their
gear. Get two Niefhoff or Electrodyne industrial strength brushless alternators
with integral regulators and your alternator troubles are over. You just won't
think about alternators anymore instead of fretting about multistage charging,
brush wear, bearing wear, AC output from diode failure, etc. These beasts just
do one thing and they do it exceedingly well: put out a fixed voltage DC no
matter what. They (both brands) seem to last forever, long after the other
alternators (Moto, Leece, Delco, Balmar etc) are needing overhauls these guys
just keep ticking. Well, you might fret about their initial cost, but believe
me they are worth it. You'll also get less RF noise with the brushless alts, a
plus for HF radio users.