In our company we use these types of branches:

• feature/fix branches
• development branch
• staging branch
• production branch

We use different merge strategies to each of them

feature -> development (squash)

development -> staging (commit)

staging -> production (fast forward)

Setting default merge strategy globally to any of them causes that for two other merges there is a very high risk of human mistake.

We would love to see some panel like for 'Branch Permissions' where you could set one global merge strategy (as it is now) and different default merge strategies for each of your branches individually.