Questions converting to a 1x9?
Do I need a bashguard? Maybe I'm wrong, but, it seems like I could just leave the larger cog in place, and that could act as a bashguard. Also, is a gear jump stop a must?
depends on how rough your trails are. 90% of the time you're going to need something to keep the chain on.
How many times have you banged your big ring on rocks or logs before? If it happens a lot then maybe you need a bashguard. It almost never happens to me so I went without. Plus the 1x9 setup probably has a smaller ring than your previous large ring, so there's less chances of it hitting anything.
If you do slide over logs a lot a bashguard will do it better than a chainring - the guard will slide across a log if you bottom out crossing a log pile for example, but teeth on a chainring will tend to bite into the log more and slow you up. With a single ring you'll always have the chain on that ring so it wouldn't bite maybe into a log, but you may damage the chain.
When you do the conversion if you buy a new ring I'd try one of the rings that's designed for single ring use. These rings have deeper tooth profiles, and lack shift ramps. This helps to prevent dropped chains, but won't eliminate them completely by any means. As was mentioned there's a good chance you will need a chain guide of some sort.