Hm, character's teams in Indigo/Orange would be like this:
Ash
Pikachu-Everything same, just it enters in it's Pokeball sometimes when it's injured...
Pidgey>Pidgeotto>Pidgeot-Catpured as an Pidgey who will evolove into Pidgeotto and later into Pidgeot during the Orange saga. It would be used more often in battles and wouldn't be released...
Bulbasaur-Everything same...
Squirtle>Wartortle-It's Squad would get a new leader, so it would evolove...
Charmander>Charmeleon>Charizard-Everything same, just it learns to listen to it's trainer somewhere in Johto saga...
Haunter-Hm, I would make Ash keep this Haunter...
Oaked
Butterfree-Everything same, just it would be Oaked
Krabby>Kingler-It would evolove into Kingler earlier and be more used in action
Tauros-Everything same
Muk-Everything same
Mankey>Primeape-Everything same, just he would keep it...
Released
Lapras-Everything same
Brock
Onix-Everything same
Geodude>Graveler-Everything same, just it would evolove...
Vulpix-Everything same
Egg>Nidoran M-He would have Nidorina and Nidorino who would have an Egg
At Pewter
Nidorino-He would catpure one who will fall in love with his Nidorina
Nidorina-He would catpure one who will fall in love with his Nidorino
Omanyte-Some random catpure before he leaved Ash and Co. during the Orange Islands...
Misty
Goldeen>Seaking-Everything same, just it would evolove
Stary>Starmie-She would have only Stary who would later evolove
Horsea>Seadra-Everything same, just it wouldn's be Oaked, would be more used and would evolove into Seadra(and later into Kingdra during the Johto saga)
Psyduck>Godluck-Everything same, just it would evolove during the Orange Islands...
Magikarp>Gyarados-Catpured as an weak Magikarp who would later evolove into Gyarados who wouldn't listen her commands at first. Misty's Charizard for short...
Team Rocket
Jessie
Ekans>Arbok-Everything same
Venonat>Venomoth-Some evil looking Pokemon who would be a Kanto version of Dustox and Yanmega... Often used together with James' Zubat/Golbat...
Cloyster-Misty originally wanted to catpure it, but Jessie catpured it before her...
James
Koffing>Weezing-Everything same
Zubat>Golbat-Unlike Brock, James would catpure a Zubat at Mt. Moon. It would evolove into Golbat(and into Crobat during the Johto saga)
Weepinbel>Victreebell-Everything same...
Both
Meowth-It can't speak or walk on two legs and didn't showed any sings of not wanting to evolove. It would be just like every other Meowth...
Ash
Pikachu-Everything same, just it enters in it's Pokeball sometimes when it's injured...
Pidgey>Pidgeotto>Pidgeot-Catpured as an Pidgey who will evolove into Pidgeotto and later into Pidgeot during the Orange saga. It would be used more often in battles and wouldn't be released...
Bulbasaur-Everything same...
Squirtle>Wartortle-It's Squad would get a new leader, so it would evolove...
Charmander>Charmeleon>Charizard-Everything same, just it learns to listen to it's trainer somewhere in Johto saga...
Haunter-Hm, I would make Ash keep this Haunter...
Oaked
Butterfree-Everything same, just it would be Oaked
Krabby>Kingler-It would evolove into Kingler earlier and be more used in action
Tauros-Everything same
Muk-Everything same
Mankey>Primeape-Everything same, just he would keep it...
Released
Lapras-Everything same
Brock
Onix-Everything same
Geodude>Graveler-Everything same, just it would evolove...
Vulpix-Everything same
Egg>Nidoran M-He would have Nidorina and Nidorino who would have an Egg
At Pewter
Nidorino-He would catpure one who will fall in love with his Nidorina
Nidorina-He would catpure one who will fall in love with his Nidorino
Omanyte-Some random catpure before he leaved Ash and Co. during the Orange Islands...
Misty
Goldeen>Seaking-Everything same, just it would evolove
Stary>Starmie-She would have only Stary who would later evolove
Horsea>Seadra-Everything same, just it wouldn's be Oaked, would be more used and would evolove into Seadra(and later into Kingdra during the Johto saga)
Psyduck>Godluck-Everything same, just it would evolove during the Orange Islands...
Magikarp>Gyarados-Catpured as an weak Magikarp who would later evolove into Gyarados who wouldn't listen her commands at first. Misty's Charizard for short...
Team Rocket
Jessie
Ekans>Arbok-Everything same
Venonat>Venomoth-Some evil looking Pokemon who would be a Kanto version of Dustox and Yanmega... Often used together with James' Zubat/Golbat...
Cloyster-Misty originally wanted to catpure it, but Jessie catpured it before her...
James
Koffing>Weezing-Everything same
Zubat>Golbat-Unlike Brock, James would catpure a Zubat at Mt. Moon. It would evolove into Golbat(and into Crobat during the Johto saga)
Weepinbel>Victreebell-Everything same...
Both
Meowth-It can't speak or walk on two legs and didn't showed any sings of not wanting to evolove. It would be just like every other Meowth...