I think that this question is interesting and has a lot of different angles to it.
First, I think it is clear the situation needs to be handled the way the sheetmakers handle it ... i.e. give the horse its number and also make a designation about the easy nature of it. I do not think it is right to give the horse a few extra points just because it could have run faster. Aside from the fact that we do not know that it is true whether the horse could have run faster, the truth is that it did not run any faster than it ran and the sheets need to reflect what the horse ran. This is no different than when a horse gets a whole lot of trouble (bad starts, checks, altered courses, etc) and you know it could have run faster. We still do not want the figure to be adjusted from what the horse actually ran.
Second, in terms of what an \"h?\" means for the next race, I think if the horse is likely to bounce off the effort, it is not relevant whether he could have run faster or not to the question of whether or not he will bounce. Reasonable minds may differ on this of course. I think that Ragozin told Jerry covers this.
Third, if the \"h?\" actually reflects a bad number for a horse, then I am more inclined to be forgiving of an off number if it is an \"h?\" (You might say how is this possible, but imagine that Curlin makes his next start in an allowance race for horses that have not won a race since October 28, 2007. If he wins by 10 with an \"h?\" but it is his worst figure ever, I am not going to be holding that figure against him. (I think Costa Rising finds himself in this scenario sometimes)).
To me the most important scenario in dealing with an \"h?\" is what happens if the figure was a horse\'s lifetime top at the time and he is now coming back to a new top? In this scenario, you may want to have more flexibility in deteriming where a horse\'s \"ceiling\" is.
I am sure there are a ton of angles on the \"h?\" I am missing here, but these are just a few the come to mind.
Also, to me this question is VERY different from the question that people who are uncomfortable with numbers often ask. For example, to me, a \"6\" is a \"6\" regardless of whether it was earned on the front end with an easy pace and a good size winning margin or whether it was earned going 5 wide in a hotly contested race with a nose margin at the finish. To me, a \"6\" is a \"6\" is a \"6\" and I do not care how it was earned. However, a \"6h?\" is something different (as is a 6 with any sort of designation).