Right off the top of my head idil, there are a couple of problems with limb regeneration...and also with the blood vessel regeneration you mentioned.
Cells can be manipulated to produce other things, but there have been problems. An early trial was to create cells that would produce insulin, which would then be injected into the pancreas of insulin deficient diabetics. They worked, and would happily produce insulin all day long...which became the problem. The production of insulin is a complex feedback mechanism that responds to the amount of food taken in, the amount of energy expended, and a few other conditions. The level of insulin produced by a healthy pancreas varies over the day, and by dietary need. These manufactured cells just put out the same amount of insulin, no matter what.
With something complex like a fully functioning limb, another challenge not yet met by scientists is differentiation. There are cells for bone, muscle, blood vessels, nerves, skin, and they must all "build" the right amount, for the right amount of time. Without a mechanism to make sure that bone cells produce more bone cells, or muscles cells more muscle cells, problems are created.
Then of course, thee is the "shut off" mechanism, which scientists have not yet found. Like the insulin cells, what would happen if the cells making the new arm or leg just kept on making the cells which they were programmed to do? You might ned up with an arm that was 6' long--wonderful if you wanted to play in the NBA, but a real bear when you went to look for a suit...
Finally, there is the matter of appropriate function. Cells injected into the heart to create new blood vessels are a woderful idea...but we can't control whether they will make the blood vessels, and whether the vessels will connect to the parts of the heart that have been damaged.
The Human Genome Project is working to overcome these difficulties, and perhaps in 30 years or so, may have over come some of them...but right now, they're still in the dark.