Some ideas from a variant I play:
IPC Income: Finland (3 IPC), Romania (6 IPC) , Bulgaria (3 IPC) & Hungary (3 IPC). These IPC income levels are fixed and do not change except for NO achievements. Any captured territories by Minor Axis nations are applied to Germany’s IPC total. IPCs cannot be share amongst Minor Axis nations or with Germany.
Germany and Minor Axis act on the same turn (so they can conduct combined attacks).
German NO: Gemamny recevied +5 IPCs while all Tripartite Pact members are unconquered, including Italy, Romania, Hungary, Bulgaria (+ Japan for global game) and Finland remains unconquered.
Unit Builds: Minor Axis nations cannot build ICs, Air or Naval bases. They can build any land unit type, Fighters and Transports but no other naval or air units. Any units purchased are placed on the Minor Axis nations home territory.
Minor Axis units can be combined with German (but not Italian) units for special abilities: i.e.: Romanian artillery can support German Infantry to recevie +1 attack bonus.
Set Up & NOs (1940):
Finland: 2 Infantry / 1 Artillery / 1 Armor. +2 IPCs when Finnish units occupy Vyborg / +1 IPCs when 3 or more German land/air units are present in Finland.
Romania: 3 Infantry / 2 Artillery / 1 Armor / 1 Fighter. +1 IPC when SZ100 is free of allied naval units / +1 IPCs when both Ukraine & Western Ukraine are occupied by Romanain units / +2 IPCs when 4 or more German land/air units are present in Romania / +2 IPCs when there is an uninteruppted supply line from Romania to all of the following german controllerd territories: Germany, West Germany / Greater Southern Germany.
Bulgaria: 3 Infantry / 1 Artillery / 1 Mech Infantry. +2 IPCs when Bulgarian units occupy Greece / +1 IPCs when 3 or more German units are present in Bulgaria.
Hungary: 3 Infantry / 2 Artillery / I Armor / 1 Fighter. +2 IPCs when Hungarian units occupy Yugoslavia. +1 IPC when 3 or more German units are present in Hungary.