This is one ive been thinking about today, and would be interested in playing it out with someone familiar with the place, year, and situation as it played out.
I would lead five or six ex soldiers, Marine Corps, seals, what have you, well armed and planned, back to Texas 1836 via illegal time travel, with the intention of aiding the defenders to resist Santa Anna's army.
We know how it ended, but my character, and the men who followed her, would aim to change that.
I would need someone familar with the movie at least, with the times, with good roleplay skill. If this is you, reply to it and lets work something out.