well we know from Empire Alone the CCAF has basicly stripped their "southren border" of mech regiments, and presumably also, after the cease fire moved a number of regiments from their fedsuns border to the "Terran front"
However many of these worlds are recently conquered and thus almost certainly need a garrison to keep order and keep the planets in line (despite having once been capellan, the stone resettlement plans means many of the worlds are going to be a melting pot mix) This means that what can be concentrated for an offensive or defensive operation is going to be considerably less. (I'd guess 10-25 regiments depending, and 25 regiments seems a little "if you lose this battle you're ******")
If I was a writer looking to reduce the CCAF's size (which let's face it, proably needs to happen) I'd have Alaric launch strikes against individual CCAF regiments crushing them as he defeats the CCAF in detail. never occupying territory or staying long in one position. A "chaos march" around Terra fits the wolves needs just fine. As I've said before Alaric basicly needs 20 years of freedom to act.