FMIR opens in the Spring of 107 during the Bellum Iugurthinum
For your information the last recorded instance of the employment of the maniple as a tactical unit is by Sallust at 49.6, when describing Metellus' order of march during the campaign of 109. Similarly we hear of velites for the last time at 49.7, notwitstanding the probably anachronistic reference to velites being deployed at Orchomenos in 86 (Frontinus Stratagems 2.3.17).
Of course cohorts were deployed occasionally as tactical units in the legion before Marius' military reforms, with some commentators arguing that the cohort developed in part because of the requirement for additional tactical flexibility during the Spanish wars of the second century. Most commentators seem to agree that the cohort most likely became the standard tactical unit during the period 104-102, with the uniformity of armament in the legion (i.e. legionaries now increasingly being equipped by the state at public expense; for precedent see Polybius 6.39.15) one possible bye-product of the enrolment of the capite censi (an innovation that was not unique and whose impact should not be over-estimated. It is certainly useful to bear in mind the hostility of the ancient sources, i.e. Plutarch Marius 9)
Marius inherited Metellus' two legions and the equivalent socii alae, with the majority of these troops having been in Africa for four years. It is therefore likely that the army was well below 'paper strength'.
Following his election to the consulship, probably in November 108, Marius was authorised to raise a supplementum and of course it was this force which controversially included proletarii volunteers, as well as a number of evocati (time-served veterans); Sallust 84.2-3 and 86.4, Plutarch Marius 9.
Brunt (Italian Manpower) estimates that Marius may have enlisted up to 5,000 new legionaries; the famous enrolment of proletarian vonunteers was undoubtedly on quite a small scale
Owing to limitations with both the game engine and available dmb space we decided not to include velites, hastati, principes and triarii. You can make your own mind up whether we have taken a liberty too far with history