Silesia has a Piast. They get a Jagiellon from Poland.
Whoops, I misread my own Diplomacy screen... they got the Jagiellon from Lithuania. No less sadface, though.
In my Austrian misadventures, I've kept looking at Influence as an idea group, but never ended up taking it... Mostly because I've been trying to stay on the princes' good sides and avoid too much internal expansion (which may be part of my problem). Looking at it now, I do like that -25% Diplomatic Annexation cost and -20% Aggressive Expansion impact. I can see that being a very valuable tool for a "Take misplaced rage-vengeance out on all of central and western Europe" game.
Considering that Brandenburg has militarily strong national ideas, I suppose I could delay a military idea until the third group is unlocked and go with something like Influence > Administrative > Aristocratic/Offensive. Bonus points if I can get Albrecht Achilles von Hohenzollern and his 2/2/1 monarch attributes killed in battle before King Friedrich II kicks the bucket.
All that said, I'm still really liking the possibilities with Bohemia, too. Might have to start a second game and give them both a try.