I'm not Japanese, but will chime in anyway...
First of all, without question the version on the left is better than the one on the right. Any Japanese person will tell you that.
Secondly, there actually is a kanji for the foot unit of measurement: 呎.
It's not in common use anymore, but I think it looks cool.
If it is important that Japanese people be able to read your logo, though, you should stick with what you already have.
As for the numbers, I think the ones you already have are fine. The ones Mike suggests are not actually older, but are used in legal documents to prevent fraud. In my opinion, they are too complex and cluttered for your logo.
So, in summary, my recommendation would be as in the attached file. But, again, if readability is at all important, then just stick with what you have.