Henry - if you did that, wouldn't you have to reduce monster damage considerably as well? I mean, I look at the last combat that I ran, and the only reason that the ranger survived was because of several surges during combat. If PC's were limited to only one per combat, wouldn't that make combat very, very lethal to the PC's?
It might make PCs go unconscious, but it'd probably only be really lethal if the DM goes out of his way to Coup De Grace.
Interestingly enough, more PCs tend to go unconscious at lower levels than at higher levels for two reasons:
1) PCs are taken out in 2 to 3 successful hits at low level, but in 4 to 6 at high. (16+4x)/(8+x) through (26+7x)/(8+x) as x (level) gets higher, the numerator grows faster than the denominator.
2) PCs have more (and stronger) options as they get higher level. The monsters gain more options a lot slower than PCs do at higher levels.
A PC can get unlucky at low level and be knocked out even with an N level encounter. At higher levels, it usually takes a stronger encounter to knock a PC out.
So, Henry's rule change wouldn't necessitate decreasing monster damage, one just has to realize that when PCs do go unconscious, that PC action economy suffers a bit if that PC has already been healed. Plus, another PC will need to use the Heal skill to stabilize an unconscious PC that has already been healed, that PC cannot be healed from range with a spell (or at least a spell that uses a healing surge, Cure Light Wounds will come back in vogue).
One other thing that Henry's rule would do is to make players less reckless with their PCs. If your PC has already used up his healing surge for this encounter, it doesn't matter if he is the Defender or the Controller or whomever. S/he'd better hunker down a bit and let other PCs take the risks, or s/he might just end up unconscious. It adds an interesting tactical element to the game when there isn't that larger safety net behind each PC.
I once ran a Leader who wouldn't heal anyone unless they went unconscious. Amazingly enough, it forced the other players to use better tactics and there were a lot of encounters where my PC didn't use up all of his heals.