Yes, we see how wonderful life is in countries with a strong Sharia influence. We see that Muslims can't even be at peace with each other in such countries. Think about how well the Sunni and the Shia treat each other.
As far as allowing Muslims living in secular countries to use Sharia... no it's not a fair request at all. It's a supremacist, preposterous and insincere request.
The wonderful life in counties with a strong Sharia is because of whom ?
Syria is a secular country. The mess there is because direct support of (Russia, China,,, ) and indirect support of (Israel, US, Europe, and tyrants ).
The wonderful life in Iraqi because US forged WMD risk in Iraqi.
The wonderful life in Afghanistan is because US decided to punish a whole country because of one person and his group.
The wonderful life in Saudia Arabia because US is protecting the royal family
The wonderful life in Egypt because US decided to remove the free elected president because he's Islamist and supported a military cope.
If Muslims living in west wants to marry, divorce, wear Islamic clothes, pray, die and buried according to Sharia is not supremacist, preposterous and insincere request.
Other religious minorities like Jews, Hindus, Sikh, Buddhist can apply their rules freely and it's respected