Our 'stirky' stalls measure 6' wide, 7' long. That's for a pair, and gives you room to go in between them to feed them, tie up / loose them etc. If you did decide to split your 14' into 3, so about 4'6" per stall, I would think you would have room to come alongside. But I would fit a post or something, or maybe two, to stop the cow being able to swing her body and crush you against the side. They can be very wide when their bellies are full! lol
Or, you could split the 14' into 2, and have a pair of stalls in each 7' wide. I'd still fit a post in the centre; that's what ours had when they were used as double occupancy. It stopped a beast on its own (no partner) swinging its body right across and pooping on the rear end of the empty half. If you fit it at the level of the front legs, there's room for you to safely go beside the beast at the level of the post
And if you were wanting to milk one of the Shetlands, you could leave her 'partner' stall vacant, and milk alongside her as I do my Jerseys.
I'm not sure how to deal with kicking ponies... I'll leave that aspect to your inventiveness!