That's true of most SR extreme cases - any time you build around one thing entirely, you CAN crossover into other stuff with a handful of low rank skills, but you HAVEN'T. That summoner needs high Magic priority, a high enough Metatype priority to get good Edge, a high enough Resources priority to service their attribute needs (like Physical boxes), and a high enough Resources priority for their foci. All in all, you're looking at about Skills E, with 6 Conjuring, 6 Binding, and only 6 more to spread amongst everything else you need to be able to do.