You can easily re spray the coating on your old tub but you will be left with that shallow unit.
Get out there and climb into some new tubs and see how they feel. I don't have a cast iron tub and love ours. It's a big soaker and plain jane but is so comfy and my wife and girls love it. It's made by a local BC company Acritec.
Here is a link to my tub. http://www.acritec.com/products/bath...city%20II.html
I choose it for the simple lines and extra width. It's 32" wide and so roomy.