Older heroes can gain a passive ability that increases their stats, only working when your hero is without costume.For example, 200 attack, 200 def and 400 hp.
Stat increases through the addition of costumes would not be blocked, and we would be able to continue playing with our favorite characters from the past.
Vela stats
4/80
743
729
1303
Medea
4/80
1019
976
1715
With this bonus vela will be weaker than new heroes but you still can use her