Can you offer any suggestions on creating bilingual documents?

Documents looks like that:
- Common title page
- Two tables of contents (one for each language)
- Contents of document, formated in two columns, left in my native language, right in other language (translation).
- Headers (numerated) and paragraphs should be in sync between language versions (despite differences in word and sentence lengths), extra white space is acceptable.
- Illustrations are common to both languages, they occupy whole page width.

Today I use huge two column table. Every header and paragraph in its own row. It looks satisfactory, but its PITA to copy and paste all those fragments into table.

I used to use two sets of connected text fields, there we easier to fill, but there were problems with keeping language versions in sync.

Do you have any suggestions on easier methods of creating such documents?