It's all going to depend on what needs to be escorted.
10 Hull Es? At least an Idris, maybe a Javelin. Certainly a Polaris or two, plus appropriate fighters and maybe a few long range missile/gunships.
A Javelin? 1-2 Idris types, 3-4 Polaris, Multiple Connies/Redeemers plus fighters (when you are escorting a Jav, you assume a combat mission, not combat free mission)
A Hull C or D? Maybe a Polaris, but probably 2-3 Wardens. Also, maybe one of the following as well: Connie, Redeemer, Freelancer
A Connie? Maybe a Super Hornet, maybe a Freelancer carrying additional cargo, maybe a Warden, but at this stage, I am not sure you will have enough money to pay for these escorts plus make money. If you are in a war zone, the Connie would join a convoy.
Honestly, it is all going to depend on how much money these trade routes make...if not much, I don't see much demand for escorts due to razor thin margins. If lots (and thus attracting pirates), then more. In system may go for Hornets, longer range may require Defenders or Vanguards. Mining missions with longer loiter times might be Super Hornets, but the ships protecting the haulers might be Vanguards or some other long range ship. Remember though, escorts are being glorified these days because lots of people only have fighters or want to justify their fighter heavy hangers. I suspect that escorts will be much rarer than people think. After all, does the M. Falcon need escorts? nope.