App Pricing: no free trial for merchants already on a paid plan

We use Shopify App Pricing with free trials on our paid plans. A merchant already paying for a plan who upgrades to a higher plan gets that plan’s trial again, minus days already used. Our trial is meant for first-time evaluation, not plan changes.

Is there a way, per plan or per merchant, to give the trial only to merchants who have never paid, or to skip it on upgrades from a paid plan? If not, could this be considered as a feature request?