This is a really terrible idea. You are wasting ability point / feat options turning a monk into a crappy fighter instead of focusing on what makes monks unique.
There is no advantage to putting points into STR as a monk.
STR increases to hit and damage
DEX increases to hit, damage, and AC
It’s a single player game, so if you want your protagonist to be the weakest character in your party, that’s up to you, but why?
Edit: I just double checked- you need to gain proficiency in medium armor before heavy and light before medium, so assuming that the final game build follows these rules, you can’t do this anyway.
You get medium armor proficiency as Githyanki though, as well as some weapon proficiencies. I knew someone will pull the crappy fighter card, but you are still a monk, with all the later features of your monastic tradition. Do fighters get that? No, they don't. Also, I agree that for your average human/half-elf/elf and so on monk there is no advantage of putting points in STR over DEX. But there is advantage of putting points into STR as a Githyanki monk, which is a +2 racial modifier. Githyanki excel at STR and it can determine not only their hit chance and damage, but also jump length, chance to shove and carry weight. You are also true that dexterity rules the AC while STR doesn't, but heavily armored solves AC completely, so there is virtually no advantage of DEX over STR in terms of AC in this setup.
