The two should be separated. It is happening
anyway but it is good to say it explicitly.

The separation of the two systems is good
both for the general chess playing public and
for the professional chess player:

the presence of the rating system for pros
reliefs the open system from the pressure
of being extra subtle, and especially from
the obligation of being resistent to the cheating
attempts. The open system would be strictly
for fun. It would be useless and even unethical
to make a serious reference to the open rating
to claim one's chess strength. E.g., the organizers
of the pro events would invite players according
to their pro-rating, and would disregard the open
rating. The only exception could be at the very
lowest entry pro level, where all kind of factors
come to into play (this is not a serious, difficult
problem anyway).

Why all this is important? Because it'd make
the open system cheaper, something like a
penny per game, per player.

***

On the other hand, the professionally rated
games would have to be played under
well understood and controlled circumstances.
The pro rating system should make cheating
virtually impossible.

This would have to make the professional rating
much more expensive per game. The separation
of the two kind of ratings would make the
pro rating more meaningful. Indeed, it is
important not to mix chess games which
have very different meaning.

Also, the data base of the pro games would be
much smaller, the relevant games would happen
less often (say, no more than a thousand per day),
hence it'd be realistic to apply a sophisticated rating
function. Such a sophistication would be essential
to professionals (but not to amateurs).

Regards,

Wlod