If your looking for suggestions, this is what I came up with.
Stats -
Health: 40
Sanity: 200
Hunger: 100

Pros -
Slower hunger drain
Faster movement speed
Cold and heat resistance
When insane gain posion damage and faster movement
Can use the Gaster Blaster attack
Can sleep at anytime
Recovers 3x as much sanity from sleeping

♥♥♥♥ -
Constant Sanity Drain
Lower damage
Gaster Blaster drains Sanity, Hunger, and Health on use

Summary -
Sans is works best as a scout. His fast movement speed, slower hunger drain, and resistance.to the tempatures makes him perfect for going on long runs with low supplies. He is best left out of a fight as very low health and low damage makes him quite easy to kill. Sans has the benefit of being able to sleep at any time to recover health and sanity. He also
gains 3x as much sanity from sleeping! This will be important as Sans will be losing sanity
over time. The knowledge that somebody is screwing with the timeline really gets to him.
When things get bad Sans finally steps his game up. While Insane Sans will move even faster and will now also deal posion damage on his attacks. Terrorbeaks will kill Sans in one hit if he lacks any armor while he is insane, this will be the hardest part about using his
true power. Sans can also use his Gaster Blaster in an emergency. This attack deals high
damage and will always posion the target. However the attack really tires him out. It
drains 50 Sanity, 25 Hunger, and 10 health.

If you like any of these ideas, just let me know!