Ligature
As far as I know, the ß has not been removed in German during the 1996 reform. Its usage has simply been harmonized: ß now consistently appears after long vowels and diphthongs. If I'm correct, we still write "Straße" for street.
The ß originates from the ligature of 'ss'. So, it would not be a big mistake to replace it by 'ss', exactly like writing 'oe' instead of 'œ' (like 'cœur' in French) is acceptable to me.
Diacritic
In most situations, dropping accents is understandable in French. It has been common practice to drop accents on capital letters on type-writers.
However, it is considered a mistake, and modern-age computers allow all types of characters, hence there is no more excuse.
And removing accents can drastically change the meaning in French:
- L'incroyable marche is the incredible step
- L'incroyable marché is the incredible market
Bottom line
Use Unicode and a modern operating system with an appropriate input method editor, instead of looking for alternatives.