Answering the question:
OK, here's the difference between the DMG set-up and the ECLs:
First, you have to understand that hit dice stack. If I am a troll with one level of fighter, I have all my troll hit dice (and abilities) plus the one level of fighter hit dice (and abilities).
In the DMG system, I am a 7th level character. I have at least 21,000 XP. If I'm being introduced to a party, that party should be an average of 9th level (my class level + 8, as per the DMG). Hit dice = character level, and the DMG factor is a mechanism for introducing new PCs.
Under the new rules, the troll counts as a much higher level character (I think that it's +12). So my 1st level troll fighter still has the same hit dice and abilities, but he is 13th level (or whatever), effectively , and needs enough XP to reach 14th level to advance to FTR 2. I belive that the PC may start with as little as 0 XP, which means a 91,000 XP gap until 2nd level FTR, but I'm not sure. Hit dice does not equal level, and the mechanic in place balances (in theory) the PC for all their career.
Now, if you want to change the ECLs, go ahead and do it. I don't recommend you work out a system for it, I think you should just just look at the player and decide then.