I've been working on a FRLG hack that takes place 5 years after the events of GSC. I just finished figuring out the regional dex, tell me if you think any Pokemon look out of place:
000 Mew
001 Bulbasaur
002 Ivysaur
003 Venusaur
004 Charmander
005 Charmeleon
006 Charizard
007 Squirtle
008 Wartortle
009 Blastoise
010 Caterpie
011 Metapod
012 Butterfree
013 Weedle
014 Kakuna
015 Beedrill
016 Burmy (Viridian Forest)
017 Wormadam
018 Mothim
019 Combee (Viridian Forest)
020 Vespiqueen
021 Pineco (Viridian Forest)
022 Forretress
023 Mimikyu (Viridian Forest)
024 Pichu
025 Pikachu
026 Raichu
027 Pidgey
028 Pidgeotto
029 Pidgeot
030 Rattata
031 Raticate
032 Spearow
033 Fearow
034 Skarmory (Fuschia city outskirts)
035 Ekans
036 Arbok
037 Zangoose (routes with Ekans)
038 Sandshrew
039 Sandslash
040 Nidoran
041 Nidorina
042 Nidoqueen
043 Nidorino
044 Nidoking
045 Cleffa
046 Clefairy
047 Clefable
048 Minior (Mt. Moon)
049 Solrock (Mt. moon)
050 Lunatone (Mt. Moon)
051 Vulpix
051 Ninetales
052 Igglybuff
053 Jigglypuff
054 Wigglytuff
055 Sableye (Mt. Moon)
056 Zubat
057 Golbat
058 Crobat
059 Oddish
060 Gloom
061 Vileplume
062 Bellossom
063 Paras
064 Parasect
065 Venonat
066 Venomoth
067 Diglett
068 Dugtrio
069 Drilbur (Diglett tunnel)
070 Excadrill
071 Bunnelby (Diglett tunnel)
072 Diggersby
073 Meowth
074 Persian
075 Purrloin (Celadon city)
076 Liepard
077 Psyduck
078 Golduck
079 Mankey
080 Primeape
081 Growlithe
082 Arcanine
083 Poliwag
084 Poliwhirl
085 Poliwrath
086 Politoed
087 Abra
088 Kadabra
089 Alakazam
090 Machop
091 Machoke
092 Machamp
093 Bellsprout
094 Weepinbell
095 Victreebel