documentclass[11pt]{article}

usepackage{luatextra}
usepackage[french]{babel}
usepackage{xstring}

makeatletter
defdelaccent[#1]#2{% #1=liste des substitutions
begingroup
expandargexploregroupsdeftemp{#2}%
delaccent@i#1delaccent@idelaccent@i
expandaftertempendgroup}
defdelaccent@i#1#2{ifxdelaccent@i#1elseStrSubstitutetemp{noexpand#1}{noexpand#2}[temp]expandafterdelaccent@ifi}
makeatother

newcommand{name}{Michaël}
newcommand{nameSA}{delaccent[{à}{a}{é}{e}{è}{e}{ë}{e}{ê}{e}{ï}{i}{ô}{o}{ù}{u}]{name}}

begin{document}

Nom : name

Try 1 : delaccent[{à}{a}{é}{e}{è}{e}{ë}{e}{ê}{e}{ï}{i}{ô}{o}{ù}{u}]{Michaël}

Try 2 : delaccent[{à}{a}{é}{e}{è}{e}{ë}{e}{ê}{e}{ï}{i}{ô}{o}{ù}{u}]{name}

Try 3 : nameSA

end{document}