Actually, high-level MBA career offices, resume help, brands, and alumni networks are only available to the select few people who are admitted to high-level programs. In contrast, consulting services are much more egalitarian. Many, many more people could afford to employ MBA admissions consultants than will ever have the opportunity to attend high-level MBA programs. If using a person's advantages (in this case financial means) was unethical, then just about everyone in the world is unethical.
Sticking with the B-School theme, it would be just as unethical for a person employed in a company with many MBAs to use his/her network for assistance with essays or interview prep. I didn't have access to that network because of my pre-MBA career choice, so no one should.
I think your service is a great public service, don't get me wrong. I'd even consider participating as an MBA2.
However, I really disagree that admissions consulting can be considered unethical. I wrote every word in my essays, developed my own career goals over several years, developed an alternative transcript, and obsessively prepared for my own interviews. A consultant helped me tailor my message to connect with adcoms and proofread my essays. If I was a consultant already, I wouldn't have needed that help.