I have what I think is a fair solution to this whole issue. I actually e-mailed WGT with this over 12 months ago, but never got a reply.
There are 8 tiers (Hack, Amateur, Pro, Tour Pro, Master, Tour Master, Legend and now Tour Legend). It is very easy and quick to get to Pro tier, and with a bit of effort and time, achieving Tour Pro is relatively simple. Because of the number of rounds (ranked) needed, it takes longer to move through Master to Tour Master, but if you want to get there enough, it can be done by level 60 quite easily.
I made Master at level 36 and Tour Master at level 55. I am still a Tour Master at level 77, and don't expect to achieve Legend until about level 82-85, due mainly to the fact I can't unlock the equipment I need until I reach that sort of level.
I might also add that I made an initial purchase of 2,200 credits (cost £10 UK Sterling), and that is all I have ever spent of my own money. All my credits are won or viewed.
My solution (based on my experience above, is to automatically up the tier at certain levels :
Amateur - level 10
Pro - level 20
Tour Pro - level 30
Master - level 50
Tour Master - level 70
Legend - level 90
Leave Tour Legend alone and wait for player to score well enough to move to the top tier.
Obviously players will move up earlier if they meet the average score criteria (as it is now).
WGT allows the system to be abused at the moment, and we all know that, so can hardly complain that some players take advantage. I occasionally get caught out when I am not the game creator. For example, I join a skins game as the third player, and don't notice a Pro/Tour Pro at level 93 has joined after me. The game creator then tees off before I can cancel. But I am better at getting out now. I will always play Master upwards, but never Tour pros lower.