Another stem diameter question (French steerer)
Your main concern of the stem becoming stuck, is valid. It requires you to remove the stem and re-grease it more often than you otherwise might. I'd recommend twice a year minimum. Sanding the stem is a viable option, first determine how high you need the handlebars to be, then rap tape over the part you are sure you want exposed above the locknut of your headset, then sand for 10 minutes, and check if it fits. You may need to sand the wedge as well. If it doesn't fit yet, sand it again and check every minute or so, it usually takes about 15 minutes or so. I've had AVA stems fail before and I was very lucky, Cinelli, TTT, and others made stems for French bikes and 25.0 handlebars, but they're getting hard to find. I prefer sanding Nitto stems as they are well made and have models to get the bars up higher for riders who need a more upright position.