Tino, I don't think that gasket is the main problem on the Windstars. The gaskets that fit between the lower intake manifold and the head are the problem. When they fail, they leak coolant into the cylinders and into the oil. That's a major problem. My mom's Windstar is actually sitting right outside waiting for me to finish reassembling it, because of that exact same problem.
If an end seal fails, it leaks a little oil out of the engine ... not a big problem. I guess you could call it an "auxiliary breather". Actually, I realized about a year ago that the rear end seal on my T-Bird is misaligned. It has been that way for 6 years, and I might lose a little oil there, but I don't think it's worth tearing the engine open.
The webpage below is about the Ford 4.2, which is almost the same engine, and has the exact same problem. You can look at the whole page:
Or just the pic if that's faster for dial-up users:http://www.leakingfords.com/leftbank.gif
One of the manifolds that I removed from my mom's Windstar looked like that, and the other one looked 5 times worse. The rubber bead that circles that port was stretched to about double its size and was all tangled up in the intake port. There were globs of what used to be oil and coolant all throughout the lifter valley. I hope it ever runs again.
I can vouch firsthand that the Windstar seals are very easy to install correctly and securely. And my mom's 96 Windstar with 100K+ didn't seem to have any leakage from that area, so I think the seals work well.
Rich, brilliant idea ... I don't think I would have ever thought of that.