Here are some suggestions-
1. Don't join Germany's war against Allies, just let them take out france all by themselves. once that's done, use one of your focus' to get a war goal or manually justify and invade them then since they're weak- Vichy cannot join any factions only be invited, and so long as you aren't at war, Vichy cannot join Allies. Or comintern for that matter.
2. Do not join Germany's call to war against Allies, but when Germany attacks Poland, justify on France manually. When the germans are going in on benelux, declare war on France, and either mass naval invade their south or north africa (french north africa has alot of steel) OR use some strategic paradrops. Since you are only at war with France for like 8 hours, You'll have naval superiority and air superiority to pull off those quick moves, wont be able to do shit once U.K joins.
3(untested). Do not join the Axis right up until Germany has conquered the benlux and attempting to break through northern france- if you're lucky, you can then join Axis and hopefully Germany immediately calls you into war/accepts your request to join them- meaning the Alps should be either not defended or very lightly defended. Hopefully break through to however much land you wish to seize.