Being quite interested in this topic myself, I'll share my own opinions... For the record, I left the "detect lycanthropes" out because it felt situational, but it'd be easy to slap-in a core race trait "You have Advantage on Perception checks made to identify if someone is al ycanthrope".
This was tricky because of the vast array of potential stat abilities it had in 2e - your "common" Lupin had +1 Strength and Con, the Wolvenfolk had +1 Strength and +2 Con, Long-Runners had +1 Dex, to just name the closest to the ultimate template - and in 3.5, they had no ability score bonuses at all. So, I just made it up on what sounded remotely plausible.
To explain the subraces; in 3.5, the "core" Lupin was based on their appearance from the Mystara Monstrous Compendium Appendix; based, I think, on the traditionalist tribes of the Yazak Steppes, it made the lupin more or less based on Native American Tribes of the Pacific Northwest. If those tribes specialised in hunting werewolves from atop the backs of giant wolves, anyway. It also acknowledged the existence of "nomads", who essentially scavenged on the fringes of human territory (only difference was favored class switched from Ranger to Barbarian), and of the civilized Lupin kingdom of Renardie, which was more of a Pseudo-France in the age of swashbuckling type culture (favored class: Bard, replaced Expert Rider with +2 to all Crafts checks).
So, with no real idea how to pull it off, I tried to make the subraces follow a similar line; rugged, honorable, grasslands hunters, resourceful and hardy scavengers, and witty, urbane, civilized individuals. I could use feedback on my efforts and I'd really appreciate discussing this race; I do own the Red Steel boxset and the Dragon Magazine issue where they were updated to 3.5, so I can share the lore from those books on here if required.
Lupin
Ability Score Modifier: +1 Wisdom
Size: Medium
Speed: 30 feet
Vision: Darkvision 60
Lupine Senses: You have Advantage on Perception checks where your keen sense of hearing and scent are relevant, but suffer Disadvantage on Constitution saves against attacks based on odor or sound, such as a banshee's cry or a ghast's stench.
Subrace: Choose between the Tribal, Nomadic or Renardie Lupin subraces.
Tribal Lupin
Ability Score Increase: +1 Strength, +1 Constitution
Plains Hunter: Your Movement increases to 35 feet. Additionally, you do not suffer movement penalties from difficult terrain in grassland environments.
Run With The Pack: You add double your Proficiency bonus to Animal Handling checks made with wolves or wolf-like magical beasts, including giant wolves, dire wolves and worgs.
Nomadic Lupin
Ability Score Increase: +1 Constitution, +1 Dexterity
Hardy Scavenger: You have Advantage on saves against disease and the poisoned effect.
Cobble Together: You have Proficiency with Tinker's Tools, and Advantage on any check made to use those tools to try and reassemble, repair or otherwise restore functionality to a degraded or damaged tool, weapon or suit of armor.
Renardie Lupin
Ability Score Increase: +1 Intelligence, +1 Charisma
A Civilised Weapon: You have proficiency with the Rapier.
Vintner's Palate: You have double your proficiency bonus to Constitution checks made to avoid being affected by alcohol, and to History and Investigation checks made in relation to alcohol and brewing.
