This is something of a gameplay suggestion, but perhaps for Rome's Marian Reforms, in EB 2 instead of first needing to win the campaign before you get the Marian Reforms, or having unbelievable luck the requirements are

172 BC
Carthage is destroyed
25-30 provinces
Must have (All Italian Cities) Some Greek Cities, all former Carthaginian holdings in Spain
Must have a treasury of one million sesterces
must have at least 6 Latifundia in Italy
Sweboz Aediu or Arverni must still be alive

To balance it perhaps The Marian soldiers should only have a discipline advantage over earlier Romans and be very expensive?