I also vote for keeping it the way it is. Give it a weird/clever name that makes it feel more deliberate..."The Slow Dissolution of the Rectangle" or something geeky like that!
For the bottom...I think you've got lots of options!
One option is to cut through the beige to make it straight and then put another strip of beige to bring it back to full length.
Or you could cut higher, through the bottom of the white blocks (so the bottoms of the white blocks would now be even but the boxes would be of varying heights) and then put your beige bottom border back on. (I think this is probably what *I* would do, but this is YOUR quilt!)
Or you could cut the beige down on the bottom, figure out what thinnest part of the beige at the bottom is and cut the beige on top to match that width, and then add a contrasting fabric to both top and bottom.
Or if you are just not happy with it at all there's always the "nuclear option" - you could just chop the whole quilt top into squares and then play with the squares until you have an interesting scrappy crazy quilt design.
But I don't think you need to get that drastic, I think it looks great just how it is.
Please post some pics when you finish it up!