Neat idea! I'd argue that the collision risk is basically zero because even though the entropy is lower, because you must validate the LLM-output anyways for two reasons:

1. LLMs might lack intrinsic entropy and reuse some UUIDs much more often.

2. Referential integrity is as important as collision resistance. An LLM must be able to reuse the correct id in the correct place.

On the other hand, using a dictionary for the ids helps with readability, but depending on the models strenghts, it might also add a confounder. After all, tokens that represent real words will probably influence the attention in a different way than random numbers.