I think a group of devout believers should make the arguments, but not call it 'reform' or an attempt to modernize Islam.Its possible that Islam maybe an evolutionary stable strategy and if that's true, it explains then why Maajid Nawaz,Irshad Manji and others face a wall.
There could be some resources from Islamic tradition that can be used by believers to end the use of hudud for instance. I wrote this last year:
I remember thinking about this several years ago: Could the law on treaties in Sharia be used to get rid of the Hudud(the penal code of Islamic law). If Im not wrong, all muslim countries have signed and ratified treaties against torture. Considering the fact that the prophet put priority of the treaty over converts who he sent back to Quraish as part of Hudaybiyyah deal, and because of the same deal, released those who left Islam, do you think it's a convincing argument against the hudud in the modern muslim world. The argument should become stronger for those who believe in the death penalty for apostasy, exactly because of the fact that the Hudaybiyyah treaty relates to this.
Also, almost all(Saudiarabia being the exception) countries in the muslim world have signed the Universal Declaration of Human Rights. The argument will not work for Takfiris, who would declare the regimes that signed those treaties as apostates, but it should work within the mainstream who believe that Sharia cannot be separated from politics
As for killing a dhimmi unlawfully, it is major sin, and the warning concerning that is very stern, as was proven in Saheeh al-Bukhaari (3166) from ?Abd-Allaah ibn ?Amr (may Allaah be pleased with him) who narrated that the Prophet (peace and blessings of Allaah be upon him) said: ?Whoever killed a mu?aahid will not smell the fragrance of Paradise, although its fragrance may be detected from a distance of forty years? travel.? Imam al-Bukhaari included this report in a chapter in his Saheeh entitled ?Chapter: the sin of one who kills a mu?aahid unlawfully.?
Al-Haafiz Ibn Hajar (may Allaah have mercy on him) said: This is how he defined it in the heading. This idea is based on the principles of sharee?ah and it is also stated in the report of Abu Mu?aawiyah which mentions it with the words, ?unlawfully?, and in the hadeeth narrated by al-Nasaa?i and Abu Dawood from Abu Bakrah with the words ?Whoever kills a mu?aahid soul that is not permissible, Allaah will deprive him of Paradise.?
Isn't Mu'ahid anyone protected by treaty. In the case of the treaty of Hudaybiyyah, that seems to be the case.
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Infact I think the rest of the world should DEMAND that that Islamic states that have signed treaties and conventions should honor their word. It should be said to those countries that not honoring treaties means that the word of Islam can not be trusted if they don't honor those treaties.