My thoughts:
1. Gluing your base to a waste block then parting your completed project off of that block saves using some of your good base wood to hold the project. Your sacrificial waste block can then be held on the spindle with any of a variety of methods. Dovetail on a scroll chuck, faceplate and screws, and a hole tapped into the glueblock th thread it onto your spindle are some of the common ones. I've used each method, depending on the project and my whim at the moment.
2. A way to make the glue block easier to remove from the base is to dish out the glue block to leave a ring of glue area with an OD about the same size as your raw base block and an ID about 1" smaller than the desired finished base OD. This will leave a ring about 1/2" wide to hold your piece. This way, you only have to part through that small ring and don't have to part all the way to the spindle axis. A deep part can sometimes cause anxiety.
3. If you choose to make the bowl (and it does look like a very good choice) but you have concerns about just how to mix maple and walnut, you might consider using only one species to eliminate one thing to have to keep track of.
4. You might even consider making it out of poplar or pine and calling it a learning experience. Then if you do something you'd rather not show off (all of us have done that), you'll have to qualms about heating the shop with it. Remember, wood is usually not like money. It really does grow on trees.