Here is what it should be:

The weapon should have the same stats as when it's used by either the engineer or the spy.So meanwhile those 2 use it, the stat for both don't change.

Further explanation:

Stats
+20% faster firing speed
+15% faster weapon switch
+Mini-crits against disguised spies (Optional)
-No random critical hits
-17% smaller clip size
-20% damage penality

The spy has 5/24 ammo and for the engineer it should be 5/200, so basically the spy and engineer hould have the same clip size, unless a bug certainly might not allow it.

Thus to finish this post, I suggest to the creator of this to create some multi-class cowboy cosmetics for the spy and engineer only, such as at least one hat or 2 to make a kit.

Well good day to y'all.