or you can grab a save file with all mons, then use Batch editor to turn them to eggs.
code:
.IsEgg=True
.IsNicknamed=True
.Egg_Location=60002
.Met_Location=0
.Moves=$suggest
.RelearnMoves=$suggest
.Nickname=Egg
.EV_ATK=0
.EV_DEF=0
.EV_HP=0
.EV_SPA=0
.EV_SPD=0
.EV_SPE=0
.Move1_PP=$suggest
.Move2_PP=$suggest
.Move3_PP=$suggest
.Move4_PP=$suggest
.CurrentFriendship=1
.Met_Level=1
.DynamaxLevel=0
as it stands, the issues you would have to fix is:
a. remove all the evolved species and
b. change all the levels to match lv 1s.