Sean,
I agree that if the rule is established in advance, the players should/would act accordingly with regard to shot selection. I think we would lose more than we would gain from such a rule, but others may disagree.
I think it's not a big issue because luck in these situations is uncommon. At the pro level, how often do you see:
1) the shooter miss an offensive shot, AND
2) leave a safety, AND
3) do so without considering that the cue ball/object ball could wind up in approximately that position if he missed?
I believe that all three of those things must occur for this shot to be considered "luck." At the pro level, these sorts of lucky shots do happen but they are unusual. There's much more luck involved in the break shot in 10-ball than you will ever see from miss/safe shots. And you're losing the creativity and beauty of intentional two-way shots if you ban them.
If you want to reduce luck, modify the break shot first. I think it's inconsistent to worry about this sort of luck while the break is still out there.
PS - it wasn't my friend who lost on the 10-ball combo; it was another poster's. On that rule I think we are in agreement. An "obvious shot" standard is not objective; I would prefer the rule that anything except a straight-in shot must be called. Everyone can agree ex ante on what is "straight-in" and what isn't.
tsw_521:
Apologies for confusing you with another poster on that "friend not knowing the rules" thing.
I appreciate what you're saying, and this same argument is brought up each and every time by players who encounter these rules for the first time. Tony hears it all the time, and his answer is the same: "you can't apply Texas Express thinking or strategies to this game. You have to think differently." The intent is to shatter the mold of Texas Express thinking, to really distinguish 10-ball as a markedly different game than 9-ball, not just "call-shot 9-ball with an extra ball." And as beautiful as two-way shots are, they are unique to 9-ball as it's played with Texas Express rules. (It's helpful to note two-way shots didn't exist in 9-ball prior to Texas Express, when the game of 9-ball was played with push-out rules.) So two way shots are an unfortunate-but-accepted casualty of this new way of thinking / strategizing in this intentionally different game of 10-ball.
9-ballers, looking to accept the game of 10-ball, have a hard time with this rule, but that's obviously because old habits (Texas Express habits) die hard. Give it time -- you'll warm up to this rule.
-Sean