Cool, that's similar to the direction I was thinking, but without many choice for amero.
I did:
1 oz Casamigos reposado tequila
3/4 oz Noilly Prat original vermouth
1/4 oz Amaro Nardini
2 dashes Scrappy's Grapefruit Bitters
I would go slightly heavy on the Nardini and maybe a bit lighter on the vermouth