replumb with pex. you can get color coded pipe at pexconnection.com or just use what Lowe's sells. You should be able to route it around and behind things without too much trouble. Connections are with Quest or Flair-it fittings or you can use a crimping tool. If you plan things a bit, you can make sure the pipe runs are easy to drain and all connections and fictures are fairly easy to get at. Use the 3/8 tubing that mates to standard half inch pipe fittings.
The quest or flair-it fittings will also work on copper tubing so you can mix new Pex with old copper if you want to without too much trouble.
Use flexible sink hookup line (I like Tru-Value Hardware's selection and type) for short runs (< 3 ft) and for the pump connections. They reduce vibration and are easy to disconnect to help in drainage.
But, if your tanks are leaking, replacing them can be a pain.
Toilet valves and complex one handle valves are most subject to freezing damage, too.