Let´s say during the Suebian Rhine crossing Ceasar is not available because his military and political career is somehow averted (maybe his political enemies managed to undermine his position). What if Suebian chieftain Ariovist conquered Cisalpine Gaul, Helvetia and parts of Northern Italy.
Would the celtic tribes been pressured to invade Roman territory ?
Could it be possible, that 500 years before Clovis (Chlodvig) a Germanic tribe manage to establish a Kingdom in Gaul ?