I'd also suggest keeping a running total of winnings including every form of the game for every player, just like the score history is kept. Once the player surpasses a certain earnings threshold, it's automatic tier up.
I have seen this idea floated around and it seems there is merit in it. I guess the threshold's may be key or being able to show an actual "profit" margin that is clearly available in the highest payout events. Or, as you suggest connecting the wins to the more lucrative and challenging events to win.
The reason I inquire is because I waited a long time before I even attempted a ready go... I stuck with free events because I didn't want to throw credits away and have to watch even more 2 credit videos which is where I build up credits for equipment and ball usage. That said, with diligence you can gradually build a heck of a credit bankroll even 2 credits a time over the course of a year.
That said, once I did start playing ready go's I found even playing reasonably well, the profit margin is rather slim and you can "increase your career earnings" while losing credits. The bigger the entry the more you can lose and still show "earnings" while losing credits.
I also briefly participated in a club where the owner enjoyed "donating" huge payouts for club tournaments. Now this was quite generous but as long as there are at least 10 people in the club, those winnings also get attributed to your career earnings. It seems this too can grossly distort one's career earnings and you are not necessarily against a field of 100 or 1000 players.
It doesn't diminish or devalue the generosity of the owner in any way, but I was looking for a group that would help take my game to a higher level in order to be more competitive and maybe eventually compete with the top players as I get promoted.
So, while I agree there is merit to using one's career earnings, I also agree how those earnings are acquired should play a factor as well. Players should not be able to in essence buy their promotion into Tour Champion or Champion by playing in a small club with a generous owner.
I would also suggest the Tour Champion tier, if opened, remain "invitation only" to prevent the issue that has arisen in the champion tier by allowing so many to exploit easy red tee tournaments to get promoted, imho anyway.