I'll try to rephrase the OP question. (In fact, I've been wondering about it myself.)
Does using an agent to get an EOS, for logistical reasons (a.k.a convenience) rather than for reasons of non-compliance with the requirements, involve any risk?
I don't know the answer, but I think it boils down to one thing. Given that the applicant fulfills the EOS requirements, the only way this can be "risky" is if the act of using an agent rather than doing the legwork in person is prohibited by law, rules, or regulations.
I do not know the answer - to answer it would take someone familiar with Thai law.
My guess would be that, given a large volume of EOS' processed for applicants who do not fulfill the requirements, the risk for someone who actually does fulfill the requirements and only uses an agent for convenience, is negligible.