My opinions on your questions, Bat Dad ...
Question #1 - A poster who was talking about varying coaching philosophies is somebody I respect immensely. And as for say a philosophy that you play your top nine, all the time, regardless of who you play, regardless of whether it's pool play or otherwise - is this something that is commonplace? Is this something that exists primarily at certain age levels? "Playing the best 9 only is commonplace in bracket play and high school/college ball, but even many of those coaches find a way to get bench players time and occasional starts, sometimes depending on the level of the opponent. It is more common for coaches to play all of their players in pool play, though not necessarily evenly."
Question #2 Is it incumbent upon any coach of younger players to develop them along with their assistants or is it the job of the kids on their own and through their parents who are spending hard earned money - as I'm guessing most of us do - to develop them through private lessons? "It is absolutely incumbent on coaches of younger players to work to develop all of their players. It's good for them and it's good for the team. If the parents want to take them to the next level, then yes they will likely need to spend and sacrifice to make it happen as well."
Question #3 - So if #2 is true it implies that coaches are not responsible to work with girls on an individual level to mentor them to become better players. "The coaches ARE responsible. If the coach says they're not, find a new coach for your DD."
Question #4 - Has 10u become far too competitive (cutthroat)? It is true that in some cases, the number of runs scored and/or margin of victory does count into the eventual seeding in bracket play correct? So going back to philosophy, if it's a philosophy where a coach is going to go after that number one seed for every single tournament Winter spring summer or fall, or is it better to have a philosophy where pool play will be used to develop players that may not see as much playing time as others? Has it always been this way if this is the way it is or have times changed? And what does 12u look like in comparison? Or Showcases? (unless for Showcases you only dress 9) "While the level of talent and play is up, I actually think that, generally speaking, coaches today are more balanced in this regard than in the past. Those of us who are older were brought up in an environment that we knew the coaches were playing to win, and that if they didn't think we were the best players to do this, that we wouldn't play, and our parents didn't complain about it either to the coaches or in front of us ... so more of us coached that way too. I think today's coaches are better about that, though of course there are exceptions and the most common exceptions tend to be at the lower age levels where first time coaches haven't figured that out yet."