You've got really good size cage!. I would think of the planting by how the sun works.
Put the strawberries on front on sunniest part of the cage and easy access, you'll be visiting those most often.
Could you plant and train the blackcurrants against the cage?..perharps all on one side, and not so that they would shade others.
Raspberries at the back..being tall they will reach the light, can cope with less sun..and again..will shade others.
As for blueberries and gooseberries..hmm...dot them about..but they don't need be in the 'best' light..though will like it...depending of the variety of the blueberry, they can grow taller than goosies..
If you use the light as your main way of thinking..then dot them about in cage and see how you have the access around them..and don't forget how much they can spread.
If needs to be..blueberries for not being thorny, you can plant them bit closer together and still able to pick the fruit.. ;) 'Goosies'=b****rd berries will shred you into pieces with their thorns if you can't get by or they are in difficult position for picking... ::) Use the poles for you advantage..they can be positioned almost in centre of some your bushes and maybe some branches tied up..like with canes for easy picking or shaping the bush.. you might need to hold some heavily fruiting branches off from ground too..;)
