There is no reason this size plane needs to be either fast or "twitchy". As for being too much for someone new, I learned on a plane that had an Enya .15. I consider myself an ok learner, but certainly not a superstar. The key is picking the right kit for the skill level, building them light, not setting the control throws too high, and remembering that the throttle has settings between idle and full

I think the biggest problem is that so many people have either moved to electrics, or have been steered away from smaller glow engines by stories of how hard they are to fly that manufacturers have largely abandoned this range. House of Balsa has severl kits that would work well for a .15 engine. Here's a couple that might be worth researching further.

Laser Stick .10 (aka Chea-Pass) - I've read that this one is fun and can be setup tame. I have a kit on the shelf, but haven't built it yet. Might start it soon, but have to finish my Pilot Hyde-Away 15, and then my Shrike 10, and then maybe my Marutaka F-4 Phantom, etc. Of course there's also the Great Planes F-15 I just bought off eBay that I've got to fit into the build schedule, but I digress.

Spacewalker - This one looks tame, but haven't built it.

I'm sure there are many more out there. I see older kits on eBay all the time.