Your first request (using coordinates to get acreage and tell if the lines close) presents us with a number of very difficult challenges. I'm assuming that what you're talking about are the legal descriptions used in plat books and titles. The problems that we run into are that these lines will vary due to features (predominantly elevation) of the land that we don't necessarily know about. We will see what we might be able to do in the future.
For now, most drawing tools can be used with coordinates. For example, if you select the Multi Line tool and then hold down the Ctrl & C keys on your keyboard you will be asked for the coordinates on where to start the line. After entering the first coordinate you can continue to use the Ctrl C keys to enter the coordinates at each "bend" in the boundary. As long as you finish with the exact same coordinate that you started with you will have a closed object.
With regards to translucent layering, you can currently create layers that are strictly patterns (with no background color). To do this, when selecting the colors be sure to select "Transparent Background" in the Pattern Selection box. I see people setting up their soil type layers with patterns only (each pattern representing a different soil type - remember that you can use different colors for the patterns). You can then show the soil type layer on top of any other layer (such as yields) and be able to see how the two relate. Translucency in general is a difficult thing to handle in Windows programming and from what we've seen, if we could add the feature it would be very difficult to get any meaning out of the maps. For now, using patterns with transparent backgrounds is the best we can do to help you.