How about making playing tall more engaging and fun instead of just punishing playing wide?
A player going wide is hardly punished, except perhaps in HRE. Once the coalition dodging mechanics have been widely known, it became fairly easy to avoid most of the penalties of going wide. All it takes is an intelligent selection of idea groups that mitigates the most obvious downsides like unrest and religious differences. The combination of several factors (Florry's iceland conquest being a prime example) can lead to ridiculous expansion capabilities.
Sadly, no such synergies exist for players going tall. There are no loops through which a player can jump to have, say, 97% development cost reduction. The best you can do is to start (or conquer) a territory that consist of farmlands, equipped with luxury goods. Only one such region exists in the world: Northern India. With a honorable mention of France, Netherlands and Silesia.
EDIT: upon further examination, I find my post to be not true.
Florence -10%
Orthodox icon -10%
Loyal Burghers -10%
University -20%
Embraced Renaissance -5%
Trading in Tropical wood -5%
Parliamentary issue "Land reform" -10%
Encourage development state decision -10%
Max. State Prosperity -10%
Full Economic -20%
If these bonuses are cumulative, I'd put it at -100% lol