What you could do for Hartlepool is this.

1 High Tunstall - Middlesbrough kept as it is but possibly becoming a joint service with Stockton.
The High Tunstal Seaton Journey renumbered to 1A or 2. Meaning that reduces the number of buses Hartlepool need for it.

3/3A already had reductions down from 15 - 30 Minutes can’t really cut it further. Putting it back to inter working with the 6 could work though. 3 would run every 20 minutes.

6 continues as now but split back into every second Journey going to South Fens these Journeys renumbered as 5 on 20 minutes frequency. 6 would inter work with the 3.

7 could be dropped down to every 15 minutes going back up to 10 at peak times.

If more drivers and better buses become available also do a 7A again which operates via Millbank Road and Morrisons M - F daytimes
This would only be temporary solutions though the long aim should be better services.

Using Saint Patrick’s could do 3/6/7 inter working.
Say a fleet of 36
5 Dart SLF
10 of the better 08 plate enviros
6 Alexander 300 ( From Stockton or Newcastle )
2 Mercedes Benz sprinters ( Teesflex)
3 05 plate enviro 300 ( from Teesside )
10 64/15 plate Enviro 300 ( From Stockton ).
This would see off the majority of the 08 plate enviros. The 59 and 61 plate Dart bodied enviros could be used in spare capacity’s or go back to Sunderland/ Shields depots for work there.

If Newcastle get 20 or so buses such as mixture of enviro 200 and 400 MMC then Stockton could get older 57- 61 plate enviros as well as well as Alexander 300 freeing up some buses to move to Hartlepool which would make the fleet more reliable even if it is still mostly older buses.