I use the novation impulse 61 for gear which is around 10kg. and within around 10 months, the stitches on the strap was torn... had to buy another gig bag.
anyway, the front pockets are well designed enough for a two cables, an effect pedal, an small-sized audio interface, and some other stuff. But for synths/ keyboards that weigh around 10kg, a bag with both shoulder straps is still better esp. you do need to carry your gear around frequently.