[5E] Jabber and Hush look away.

hey everyone!! i'm writing a campaign centered around these incredibly powerful magical artifacts that are designed for each of the players (a furbold paladin, a tabaxi monk, a kenku sorcerer, and a dryad druid). im trying to come up with good, useful passive effects that will always be utilized and also a "charge" effect that will be very very powerful.

for example, the item i have for the kenku sorcerer allows him to add his proficiency bonus to all int and wis checks (he has really bad stats for both) and has 3 charges that, when expended, allow him to "lift the kenku's curse" meaning he can speak normally (he usually has to mimic other people), come up with original thoughts (which kenku cant do). mechanically, i was thinking this allows the player to have his int/wis mod become his proficiency bonus+his spellcasting mod. i was also debating on having him do a con saving throw when he wants to use it.

for the paladin i was thinking having a +2 or +3 weapon that also acts as a +2 or +3 holy symbol, but i cant think of a charge power for that. for the monk i was thinking something that allows him to not have disadvantage on any saving throws and as a charge maybe he can sub any mod for any other? (i.e. he can sub his charisma mod with his strength mod).

they were going to get these gradually throughout the campaign and someone pointed out the balancing issues with that (the first person to get it has a huge advantage) so i was thinking of them gradually getting more powerful the more artifacts they get. so i was gonna have the kenku get his first, but maybe i could change the item so that it lets him add +1 to his checks as a passive and he gets no charges yet. and then when the next person gets theirs, his gets stronger so it does +2, and so on until everyone has theirs all at full power. any suggestions for magic items or balancing is greatly appreciated!!!