Is a Theravada Buddhist permitted/able to take a Bodhisattva vow?

This is a sister question to this one . Suppose a Theravada practitioner decided they wanted to take a Bodhisattva vow, could they (and remain Theravadin)? I guess there are a few of components to this question: 1. Does Theravada have scope for individuals to even make the Bodhisattva choice at all when the time comes? 2. Even if it does, does it then allow for individuals to make a promise, in advance -- i.e. to vow -- that they will make that choice at that time? 3. Finally, even if Theravada sees both choice and vow as being possible, does it regard people who make that vow as remaining as Theravada practitioners, or would they be seen has having moved into Mahayana?