So I wanted to make a comparison between Pokemon from current Sinnoh (via Platinum Dex) and Pokemon which are native to Hisui but got extinct later on (and do not apper in Sinnoh). I took out the Hisui starters (as they are natives and also because the numbers will not add up) and considered Space-Time Distortion Pokemon as non-Hisui exclusive (with the sole exception of Magnazeone as it appear in the wild at Mount Coronet in Legends).

So here's my list:
1. Seaking - Basculegion
The common fish-Pokemon
2. Noctowl - H-Braviary
Bird with Psychical powers
3. Quagsire - Parasect
Quite weak, marsh-like Pokemon which does not seem to be the sharpest (I know it might be a stretch)
4. Azumarill - Sylveon
Rabbit-ears, popular and Fairy type. I still hate that Sylveon was cut from BDSP. If you don't like Azumarill-Sylveon you can switch Sylveon either with Female Basculegion or Alolan Ninetales but I like Azumarill-Sylveon comparison.
5. Houndoom - Ninetales
Fire-type canine (I left Arcanine for later)
6. Milotic - Walrain
Strong Hoenn-based Water-type
7. Altaria - H-Goodra
Cute Dragon-type
8. Absol - H-Zoroark
Both are mystical and somehow connected to disaster. Both give quite a similar vibe.
9. Tropius - H-Electrode
Grass Type, one is a fruit while the other an Apricorn
10. Girafarig - Wyrdeer
Normal/Psychic-types connected to Johto (1 Johto native while the other evolves from a Johto Mon)
11. Pelipper - Overqwil
Both are quite oval and are available close to the sea (and are quite common there)
12. Medicham - H-Liligant
Slender Fighting-Type
13. Weavile - Sneasler
Self-explanatory
14. Scizor - Kleavor
Also self-explanatory
15. Porygon-Z - Ursaluna
Strong Normal Type which evolve from strong Pokemon. Also nice Science/Technology vs Nature
16. Rampardos - H-Arcanine
Rock-types with strong Attack
17. Bastiodon - H-Avalugg
Rock-types with strong Defence and 4x weakness to fighting

Feel free to comment:-)