Increasing the Character limit in Opentype

What you ask has been deemed not possible, simply because the 64K glyph limit cannot be raised in the context of the 'glyf' or 'CFF' tables of the OpenType Specification. This was investigated a few years ago, and I was part of that effort. The short answer is that such a change would need to touch far too many parts of the OpenType Specification, and would create incompatibilities. The font formats that are used to produce the 'CFF' table, meaning name-keyed Type 1 fonts and CID-keyed fonts, have similar limits that carry forward to the 'CFF' table.

The solution that came out of those discussions was to standardize a composite font format that uses a virtual font resource that references two or more component fonts. This work has been done, and was published earlier this year as ISO/IEC 14496-28:2012 (Composite Font Representation). See: http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=59240

The first OS to support CFR objects is Mac OS X Version 10.8. I wrote about here, which includes an "All of Unicode" CFR object and the component fonts that it references: http://blogs.adobe.com/CCJKType/2012/07/cfr-support-in-mountain-lion.html

I hope this helps...