Is it possible to have a Modifier with Promotional Goods and Terms Substitution lines?

We have a promotion that allows customers to buy X get Y, AND receive special Payment Terms of 3/10 NET 120. Unfortunately there seems to be incompatibility between the Promotion Goods modifier line and the Terms Substitution Modifier line.

I have done extensive reading about change the Price flag to Partial PRice, but then our Free Item is assigned a value, which defeats the purpose of the promo.

Are there any solutions? This doesnt seem like an unusual request. If more information is required, please let me know.

Thanks,

Kailey