If that is the set up you want, why not just play the 41 scenario?We might get a little OT, so I´ll try to cut things short: Base IC 314 (no IC built, only infra), available 213 (-68% peacetime modifier). Most relevant techs have been researched (90% speed), 4 lv.IV CV´s built, several lv. IV CA´s, CL´s, DD´s, sub´s. All Pacific islands have GAR, the 4 most important ones are stronger and fortified. Airpower is somewhat weak (only a few INT built), only defensive ground forces. That´s pretty much the situation of the US before they entered WW II. They are not likely go into the offensive immediately, but with another 213 IC to come when the war starts they should be able to turn the tide within one or two years.
I do a HUGE ic build in prewar years. 12x5 to start with more ic built from the increased ic. I don't build many units while Garner is in office. I shoot for 400 base ic. IC was the defining factor of the USA in WW2. I emphasize that. 314 base is too close to what Germany and the Soviets can have. The USA should have a major IC advantage over the rest of the world.
To prevent prewar unit spamming, might I suggest that Garner's unit cost Malus be substantially increased while leaving the USA the ability to substantially increase non military builds(ie ic, infra, refineries etc....).