I'm generally against WoW style gear score checks. In the spirit of providing constructive feedback, I'd really like the codex check for certain hard modes. If someone's queuing for LI HM, it'd probably be wise for them to have first gotten the codex entry for LI SM. At the very least you'd feel comfortable that this toon has gone through the content at some point in time. The same would apply for HM EV/SM, it would be really nice to introduce those into the Group Finder as queue choices, but requiring the existence of the story mode codex entry would be awesome.
Just my 2 cents
Only reason I don't like this idea is because gear requirements for SM are clearly significantly lower than for HM. I don't even run HM for the gear drops myself, mainly only run it to get my weekly and help out friends. I am not saying someone needs to be checked as full rakata or even columi to run LI HM, but someone with 50 mods should not even be queuing for LI HM let alone getting in to one. I don't like people who leave/quit a group because they don't like the FP selected, but in this case ..it's understandable. But yes, them running LI SM prior would be helpful still.