If Tetsuo has Boost tokens but no Blob tokens, can he do damage? He's not in either of the lists under the Boost Icon section of the rules, so I wasn't sure.
For a boost token to add damage to a damage ability, the ability must first do damage. If Tetsuo's character has no blob tokens, he cannot do damage. This would be the same as putting a boost token on GLaDOS. It has no effect. You still put the boost token on though as there is the good possibility that Tetsuo will be able to do damage in the future.
We must move forward, not backward, upward, not forward, and always twirling, twirling, twirling towards freedom!
The part that really made me question it with Tetsuo is whether there was a distinction between not being able to do damage and doing zero damage. A similar "zero damage" situation comes up if Mega Man copies a "1 damage" ability.
Your explanation covers it well, and makes it clear there is not meant to be a difference, but it may be worth noting something about that in the rulebook when do a rewrite.