About homeland-recruited legions...

[Bonny]

Correct me if I'm wrong but I understand that if I recruit a legion in Roma city and then ship it to, say, Africa and they suffer casualties the only way to rebuild their strength (retrain) is to put them on a boat back to Roma. This means that distant provinces will feature few, if any classical Roman legionaries as those will have to be withdrawn very often because we don't want them to bleed white.

No, Rome is not the only town where you can recruit your legions. Most of your homeland regions in Italy with a high enough factional mic can train your facional units. Try the recruiment viewer (dl link in the stickied thread) to see what you can recruit where.

Later in the Game the Marian and Imperial Legions have a far wider recruitment zone than your Camillan or Polybian troops who are bound to Italy.