Schneider Electric has a good line of motor starters and protectors. I use the Uline units. They are modular and have all the features you will ever need.
http://www.schneiderelectric.com
In a former job, I worked with this type of application. First, forget the load cell and use a small dancer.
Use the dancer to regulate your tension.
The position of the dancer will provide a reference for your takeup (P control).
The system will operate as follows:
1 - Payoff system will...