I used ヲ instead of ウォ in my name in my hanko. It’s katakana, not hentaigana but you don’t see it except in old documents when they used to use katakana for particles (it’s equivalent to を). Saving the extra character meant I could get it made in ten minutes instead of one day. It sometimes gets comments when I use it.

By the way, there’s no requirement that your hanko matches your name and they only need to be registered for large purchases, like a house or for business use. They are however kept on record by your bank and sometimes compared digitally. By law foreigners can always use a signature instead of hanko but it’s not recommended as the comparison will often fail. On the other hand, online banking ans ATMs are good enough now that it’s been a good five years since I set foot in a bank.