You seem to have a level head, meaning you understand that a Mac-26 is a below-average powerboat, and a near-zero percent sailboat.
But your next idea is a very heavy sailboat that takes a gale to move it and is slow, whether under power or sail (and the Gulf in summer is light-air city).
Since I lack original ideas, I'll leave it to others to give you specifics, but there has to be an happy medium here, lightweight enough to power at 7 knots not 4, and a decent sailor once you finally get out of the bayou/channel/whatever?
Maybe a Ranger 27?? Or a Merit 25? I don't know, except that so far you've chosen boats way off the middle of the curve. Find something in the middle. But don't expect any decent sailboat to make over 7 knots under power (especially at today's fuel prices, but even when gas/diesel was cheap), it just ain't going to happen.
SailingDog through his answer above, reminds me I have limited myself to monohulls, which is my own tunnel-vision. But I like a fast, quick-tacking boat upwind, so that's where my dictionary starts and ends...