Has he considered applying to be Advanced Camp/CLC/LDAC cadre? This gets them onto active duty shortly after commissioning too. They then have priority for BOLC because they have already been accessed onto AD.DS told Jan 2018 for FA. Not happy as he wants to start ASAP. Looking into either gold bar and or trading. If neither of those work out he will get a short term job. If any FA folks want to trade shoot me a PM and I'll put you in touch with my son .
An issue with GBR may be his assigned BOLC date. I can't find the regulation or guidance but as I recall AD GBR recipients must have a BOLC date within 179 days of their commission date, maybe less. Though I had never heard of it before, last year some cadets may have been prevented from participating as a GBR if their BOLC date is in the new fiscal year due to budget restrictions.
71E Clinical Laboratory Scientist? I haven't seen it from ROTC or a SA but it is possible if they have the right degree and possibly a certification like Medical Laboratory Science Certification as part of their degree completion. They would go to the Med Services BOLC and then on to a BOLC B training for Lab Officers. The Army has a very long training pipeline for these officers. Edit: Medical Technology Certification also likely meets the criteria.