Well, point 1, these changes that you deplore have not resulted from rules changes, but from the ABSENCE of rules changes that would have and could have prevented these changes in the game from occuring.
While not wishing to be dogmatic about it, I would agree with you that the game is more enjoyable with identifiable talent than with anonymous talent. If each team has 5 starting pitchers and those pitchers pitch regularly into the late innings, that makes the talent more identifiable. If a team uses 15 starting pitchers and none of them pitch 180 innings a year, the talent is more anonymous. So I think you're right about that.
As to how to make that happen, there are 1,000 ways you can do that, 1,000 rules changes that could push in that direction. Suppose, for example, that the league were to make a rule that for every game in which the team pulls his pitcher out before the pitcher has pitched 6 innings, the team owes $100,000 to a league fund. ($100,000 is not an overwhelming amount of money in a league in which the best players are paid about $200,000 a game.) Suppose you have that fund, and that fund is then distributed at the end of the season based on how many games the starting pitchers have pitched at least 7 innings, plus the number of games in which the starting pitcher has pitched at least 9 innings. So. .you want to take your starting pitcher out in the 5th inning, OK, but it costs $100,000.
Without looking up the data, we might guess that an average team now pulls its starting pitcher in the first 6 innings about 50 times a year, which would cause a fund, at the end of the year, of $150,000,000 (150 million). Realistically, a team which pushed its starting pitchers a little bit deeper into the game could probably make a profit on the season of $12 to $15 million, I would guess, while a team that liked to jack around with its starting pitchers could lost a similar but smaller amount (smaller, because these rules in the short run would put most teams on the short side of the ledger.)
A $12 to $15 million profit in a season is meaningful to a small city team on a budget. The question then would be what happens next. If that team feels that the policy of staying with the starters has hurt them otherwise, then they'll abandon that policy. But if they find that it doesn't hurt them, then they will stick with it, and other teams will say "Hey, it doesn't seem to work against you to do that; let's try it."
There are many other rules you could make. For example:
1) When a team makes a pitching change in the first 7 innings of a game, the next pitch is recorded as a ball. In other words, make a fifth-inning pitching change, the next hitter starts out 1-0.
2) Make the number of innings pitched by starting pitchers a tie-breaker for post-season position. In other words, if Texas and Seattle wind up the season in a tie, both teams 93-69 or whatever, then the position goes to whichever team has had more innings pitched from their starting pitchers.
3) Each team has a budget for 5 starting pitchers in a season. For each game started by a pitcher who is not among the top 5 on his team in starts, the team pays a penalty of $400,000, with the money going to charity.
In other words, if you have a team lilke the 2006 White Sox, who got something like 159 starts out of their top 5 starters, then they would owe only $1.2 million into the Greg Maddux Charity Fund. But if you have a team like the Royals, who puts out there a new starting pitcher every day, then they might owe $24 million, maybe. You'd need a codicile in the rules that a game in which the pitcher "starts" but pitches only 2 innings is not credited as a start for purposes of the Greg Maddux charity fund.
4) Create league and team awards for the pitchers who pitch the most innings. Give the Steve Carlton Award to the pitcher who leads the league in innings pitched.