Now don't rush. But consider getting an overview of the market for the best keyboard-layout for your needs. I don't know how the upright japanese ones are utilized; on the contrary I can only compare DE-qwertz, EN-qwerty and FR-azerty ones, and of those the latter fits bäst. This was an DE-Umlaut ('ä') typed directly from a qwertz-pad.

It brings comfort and at least short-term usability to have the keys signed. For instance I'll now press degree °, the pound-key # and alt+234 oops, correction: alt Gr+234 ²³¼. That's still not what I wanted. Let me see.. ⅛£¤ nice, but not what I want. ⅛£¤, hmm - :... I'll take a quick search on ascii and browser-input ..

Wikipedia says
- press+hold 'alt'
- press '+'
- enter 'alt-code'

I want the 'alt-code' 234, really big, let's say 168px, with a leading colon:
:hm,
I am close to giving up, .. I give up ... I guess this browser (firefox 3.6.12 of the respective mozilla-foundation merchandized developer-community) uses alt+'1,2,3..' for tab-switching with the cost of not being capable of a common input-method for alt-codes.