I dont know about you, but I don’t mind when devs re-utilice AoE2 voicelines, infact, I do quite like it since its my second favorite AoE, but if there is one thing that I dont like is when more than 2 units use the same voicelines.
So here I have some easy to implement ideas to improve this situation. 
Hospitaler: I suggest him to have the AoE2 sicillian voicelines to add more personality to the unit (and also the doppelsoldner voice lines are used by 3 units, wich are him, the doppelsodner and the new teutonic order musketeer, but i also dont like it because the hospitaller is a another heavy infantry unit with a sword just like the doppelsodner). The sicillian voicelines could also be a nod to the fact not only malta is quite close to sicilly but that the order historically recieved a lot of support and influence from the sicillian kingdom. 
(little sidenote: I actually had this idea since the release of the knights of the mediterranean dlc, but I was so shy back then that I didnt share this little idea for the hospitaller 
)
*USA:
Right now this civ reutilices quite a lot of voicelines and it feels weird but i have a solution that is quite easy to do
Owlhoots: they should use old legacy english speaking chayton voicelines
Minutemen: Right now he uses john black voicelines which are also used by the Regular, my idea is that the regular should keep them while the minutemen can have Nathaniel Black voicelines
State Militia: He should have some other voice than the one’s that the Sharpshooter uses, so why not using old Custer voicelines, (which are used by some units like the cavalry and the artillery in the Battle for Orleans Historical Battle)
USA REV Sharpshooter: He uses the same voice line’s that the state militia uses (wich he also shares with the sharpshooter but with the pitch increased) my idea is for him to have the new chayton black voicelines
Cranequier: I suggest that he should use the burgundian voicelines from aoe2 as the unit itself is quite archaic and also because of the fact that he also utilizes the same voicelines of the Royal Horseman, the Royal Dragon, the Zouave and the Napoleonic Cannon uses (also the french spy 
)
Mongol Explorer: He should have the aoe2 mongol voicelines
Jat Lancer: He should have Gujarati voicelines from aoe2 
Gallowglass: i suggest to change his voice to morgan black voicelines (maybe with the pitch a bit lowered or a bit increased). Right now he uses the celtic voice lines from aoe2 that the scottish clansman also uses, so it would work to differentiate it and make the gallowglass more special and different 
Mapuche Bolas Rider: I reccomend to use the mapuche voicelines from aoe2 to add more distinction and differentiate him from the infantry clubman 
Conquistador: I would like him to use the aoe2 spanish voicelines because the unit itself is something of a nod to the original aoe2 conquistador unit and it would be quite charming (rn he uses the rodelero’s voice lines)
Order Musketer: He should use one of the under-utilized voicelines like the war wagon’s (rn he uses the doppelsoldner Voice Lines which are also used by the well, the dopp and the hospitaller)
Knight Brother: It would be lovely if he uses different voicelines than the blacknight (which the chevau-leger also utilizes) maybe he can use the Jaeger Voice Lines
Mayan Villagers (from mayan rev): They could use aoe2 mayan villager voicelines
Cruzo’ob Infantry: Maybe he can use the AoE2 mayan military voicelines as the unit itself is a bit different from the mexican soldado 
*Maybe the Thugge and/or Dacoit can have the Hindustani voice lines from aoe2. I dont certanly know 
*
Tiger Claw: Maybe he can use either AoE2 bengali or dravidian voicelines? but im unsure* *
(Cossack Rev Settler) Chern: he can maybe use AoE2 slavic villager voicelines? i dont know for certain*
*There is an unused celtic villager attack voiceline that the Lowlander should definitly use
Ninja: He can use the aoe2 japanese voicelines (because rn he uses the same voicelines that the ronin and the wokou variant uses)
(on a little sidenote: I heard that there is a japanese version only of the asian dynasties dlc that used different voicelines for the units but im not sure about its existence )
As you may have noticed English is not my first language so I hope i made myself clear, thanks for reading and have a nice day 
(I hope the devs implement at least some of this please 
)