I would have:
Priority Pattern Replacement Provider Active
10 _#2. ${EXTEN:2} engin account Yes
20 _#3. ${EXTEN:2} blah account 3 Yes
30 _#4. ${EXTEN:2} blah account 4 Yes
etc
999 _xxxx. ${EXTEN} PennyTel account Yes
Dial plan 999 is the default route everything else to PennyTel. The reason it is 4 digits in size (_xxxx.) is to not interfere with VoXaLot service numbers (3 digits).
Note: Reason for the priority gaps of 10 are to allow easy modifications and insertions to be made. A bit like programming in BASIC