We've got a handful of dudes your size, most of them can handle most of the system pretty well, and the one thats put effort into his flexibility (edgar) is your size but has the flexibility to do just about anything in the system. It takes more work on your flexibility-- but its still there to be had, your body still has the potential to develop all the flexibility and dexterity you will need. Its just the more you put in, the more you will get out. If you stretch twice a day everyday, when you get up and before bed (and I mean real stretch, slow, holding the positions, LOTS of breathing (breathing MAKES stretching work) and before and after training, your flexibility will grow in no time. If your willing to master your diet and trim down some inflammation (removing things like sugars, gluten) your mobility will increase a ton on top of that.
But if anything, just repping the techs constantly will improve your flexibility a bit, but real stretching as advised. Angles and shapes can replace flexibility in alot of jiujitsu