Using the ankle and foot for venipuncture and IV therapy is to be discouraged because it is a weird thing to do, the feet are relatively thick skinned (deeper epidermis to clean and puncture) and the ankles and feet are hardly as clean as our arms, wrists and hands. So yes, perhaps infection is more likely, especially in the relatively poorly vascularized (diabetic and PVD). So use those swabs and give them lots of time to work. I use betadine followed by alcohol if I must go there. There is no evidence for any of these concerns, the betadine/alcohol makes me feel better.
However, it is simply an urban myth to suggest drawing blood from an ankle or foot increases the risk of DVT. I heard this yesterday at the hospital, it didn't make any sense to me and I've just searched it now: NO evidence for this claim. I did find: Phlebotomy Tools of the Trade: Part 3: Alternative Sites for... : Home Healthcare Now
But can't read on after the first page with this link. I suspect there are claims to "beware", but there is not evidence to support this belief, nor any rational I can understand or believe. That said, if it makes you feel better, I'd be happy to give you an order for it. Then I'd learn our poor patient is not easy to get blood from and I'd have the opportunity to remind you to use extra precautions sterilizing the site.