If he learns Drain Punch (Fighting and Grass give him decent odds) I could see him pulling off a nice set with Leech Seed, Spiky Shield, and either Substitute or a coverage move. Failing that: hopefully a good boosting move like Bulk Up or even the coveted Shell Smash. Wood Hammer and Earthquake are confirmed, if he gets more solid moves like Mach Punch or Close Combat he could do alright for himself. Great bulk and solid attack.
Also I love this guy. Really happy with how he turned out. The armored warrior theme is nicely executed and I like the chestnut shell combined with the influence he seems to get from glyptodonts.