It's not just the classes, it's the talent trees, and the "class skills" (those "increased costs") you mentioned, and if I'm not mistaken the XP cost to access each new class.
By RAW this is true. However, there's no reason you can't house rule easier access (aka, lower XP cost) to other specs. For my own campaign I first asked everyone if they'd be willing to be Force Sensitive. They were, so they all got the Exile tree for free (basically a 20XP bonus on top of initial chargen). Then, because the players were all new to the game, I let two players completely redo their characters using different careers so that they ended up with the same skills and talents, but had a clearer road ahead for the concept they were after. Finally, I gave them a discount on a new spec (free for career, 10XP for non-career) provided they had at least two 25XP talents in the previous spec. All this adds up to far less than the "Knight level" bonus you can give for advanced characters, and it prevents cheap XP Talent skimming.
There could be plenty other solutions. Basically, there are a lot of ways to resolve this issue within the current mechanics that would be simpler than inventing a whole new way to control Talent acquisition and progress.