"A massive pack" would be nearly impossible since that would take the devs a lot of time, thus money. Don't expect a DLC of rolling stock larger than the BR Heavy Freight pack. I mean, a massive pack, I see that as like 20 locomotives. That would maybe cost 100 euros to buy. Not a lot of people are willing to pay so much for a single DLC. They'd rather buy locos seperately so they can choose which locomotives they want.