Re: Advice On a Custom Rifle.
jdm, I would suggest a custom built from the ground up. Keep your scope if you must, but that is a heavy scope, and there are others too choose from that will allow you to kill big game without the excessive weight.
Sell the Medalion, this will fund the custom action for your rifle.
The build, to be lighter, will need a composite stock, preferably using carbon fiber for strength and light weight. I shy away from the ultra light weights as they tend to be very petite (ie fragile)
Of the many custom actions, choose one with your smith that will fit your cartrige and be a bit lighter than the others, while still maintaining quality.
Determine what your effective range needs to be and with the experience of your smith choose a barrel contour that will provide the needed consistancy/accuracy and weight parameters of your build.
On cartiges, if your faith is a bit lacking in the 7wsm being around and available in 5 years, I'm not sure why you would choose the 300wsm. It could very well be in the same boat. The 300 win mag may be a better choice, due to the availability and multitude of availabe factory ammunition.
I hope this helped in your decision making.