Gil will murder Siegfried even without Ea and SNI,why? simple....
"GoB"
Mind you even Armor of Fafnir is strong,its have a fatal weakness,his back.So omnidirectional GoB will destroy Siegfried,the front is safe sure,but what about back? an stuff suddenly stab his back,game over,there is Enkidu too altough Siegfried didn't have any divinity its will helping Gil slightly.Also the GoB may have an anti-dragon/dragon slaying weapon in his GoB.
And you make them bloodlust which make Siegfried impossible to win,serious Gil=death to you,he's ge title "strongest servant" for some reason.
Because this Kavacha Kundala and God Hand is beter than Armor of Fapnir,KK make you reduced all weapon to 90%,GH while is B rank is broken,if you fail to destroy all of his life,he will ressurect and immune to your attack.Armor of Fapnir just null of any attack bellow B,and reduced the A rank attack to E but if you're superior enough you can bypass that armor,i mean can he survived barraged by any A rank NP or above,nah i think not,while GH and KK can.
Siegfried is strong yes,but he can't competent with another god tier servant like Gil,hell he even can't defeat Karna too,if Karna is serious then GG Siegfried.