I'm coming out of lurking to post and say that just today, I got my waiver approved to come in to the Nuke program from STG. I'm 26 years old, a ding on my criminal record, and scored a 99 on the ASVAB and 78 on the NAPT. I also have a B.S. in Ag. Economics from Texas A&M. It took pulling a lot of strings, long conversations with the recruiters and nuke coordinators, writing a rather serious essay, and two waiver submissions before it happened but its possible. Put the upmost effort in everything you can control such as tests, essays, and creating a good rapport with the nuke coord and recruiter.
Best of luck to you.