As a long time helicopter logger and also involved with the Wessex before Bristow grounded them, the Wessex is probably the worst helicopter type I could imagine to log with. I have operated and been around most types involved in these operations and the learning curve for each model is immense as you figure out the weaknesses in airframe, drivetrain, engines, rotor systems, electrical and every other system on the machine. Much of this isn't necessarily safety issues if proper and adequate maintenance for the type of operation is developed and adhered to, but never ending maintenance, parts and downtime will rapidly render the operation uneconomical. As there is no history of logging with the Wessex, you will be developing it as you go - a very demanding situation.
I have watched a number of S58T's (and piston ships) logging, all with zero long term success - they were just perpetually broken down and suffered major structural issues. The easiest way to figure out the real world experience in this instance is to let them go and log with it and see how it works out, but I personally believe the outcome is entirely predictable.
Oh, and one last consideration from the history of this genus - just read this accident report, which was pretty much the END of helicopter logging activities with the S58T, after the Main Rotor Mast failed in the hover and the Head flew off. This is one of two pilots I personally know who suffered main rotor mast failures with head separations, that walked away and live to tell the tale.
https://app.ntsb.gov/pdfgenerator/Re...Final&IType=LA