Take the Mercedes-AMG 53 I6
And put it in the Vantage with the new toned down styling
Offer it with the manual or the automatic. Make the exhaust a lot less muffled so it has a sound more reminiscent of this:
Drop the price by $25,000.00 Call it the Vantage 3-Litre Sport. Then put that engine into the DBX base model until Aston has their own V6 fully developed.