The Federation - and the Empire before it - are both home to Archduke Charles, the archenemy of Napoleon himself, and General Skala, who gave his life alongside his men defending democracy from the autocratic and imperialistic Russian Czar that dared to test the mettle of Danubian men in the field. With determination and skill, we could easily hold our own against the enemies of the Federation.
However, I believe that the Federally maintained field armies must be expanded in size and scope, as, before the war, the largest independent field army under the banner of the Federation numbered just 18,000 strong. Either these armies must be expanded themselves, or the commands of several generals can be fused with each other to form fewer, but much larger - and, theoretically, much more capable - independent units that could deal with another invasion from Russia should it occur yet again.
We could also - possibly in combination with the above consideration - reform the hierarchy and organization of the Federal Army into a Napoleon-era French-style army, with an Army divided into several successive smaller corps which have the ability of operating independently should the situation call for it. Of course, this system could be refined and tweaked to fit the needs - strategically and logistically - of the Federation and the geopolitical situation of this Continent, but the suggestion stands.