Well as of now the Garlean Empire is basically almost gone due to internal conflict for the right to rule, Legions are now splitting up into their own factions, Zeno's mindless slaughter of any resistance to the throne, and Civil War has engulfed most of Garlemald for areas around the Capital between Legions who do not acknowledge Zeno's rule. Even with Zeno control over the Capital, many other Legions are just trying to claim territory now and ignoring Zeno's new role as Emperor.
At this point all these side stories involving the Garlean Empire's Legions are more about finishing off the only remaining Garlean forces in the way of getting into Garlemald now. With Bozjan claimed by Map 3 of Save the Queen Storyline, they will finally have a Eastern side front to enter Garlemald with Doma and Resistance forces while on the Western side we have the Eorzea Alliance after they deal with the Weapons.
We can basically say the Legions are mostly Warlords at this point trying to claim their own territory and rights to rule over them.
IVth Imperial Legion follows Gabranth in the Eastern side of the push into Garlemald.
VIIIth Imperial Legion follows Valens van Varro in the Western side of the push into Garlemald.
Zenos has claimed the Captial but his progress will be shown through the MSQ in 5.4 to 5.55.
We can assume by 6.0 both Eastern and Western fronts will be taken no matter what regardless of the WoL participation in them or not due to how important both sides is required to claim their locations if they wish to finally attack the Garlean Empire at the heart of their Capital.
However, story wise I can only assume casualities may be reduced if WoL did take part in those efforts compared to WoL not being their causing them to sacrifice more soldiers since they don't have the Echo.