It is a summon jutsu by name and by nature, and the mechanics of it are as clear as day. Again, you seem to be relaying your own thoughts whereas I have canon showing Kabuto performing the Kuchiyose no jutsu. You seem to be under the impression that the seals in the person's head are necessary; they are not. They are simply there to suppress the emotions of those who are unable to act autonomously. The contract seal removes the control the summoner possesses over the summon. If such a seal is used on Orochimaru, any and all control he has over Shodaime and Nidaime will be removed effortlessly. There is no evidence for your point regarding Madara; he summoned the Kyuubi and died many years later, yet, when he was summoned, he tried to then re-summon Kurama (not realising it was inside Naruto), implying that the connection between the two remained (even after death). This actually goes against your statement regarding the matter. The effect of the contract seal on Orochimaru would be exactly the same going by what has been canonically stated.
Orochimaru does not possess the feat of summoning. When in this manga has he ever summoned Uchiha Madara via Edo Tensei?
Again, you are going against what has been canonically stated. The contract seal removes the control the summoner has over that which has been summoned, and Edo Tensei, as a Kuchiyose no jutsu, is not exempt from this rule. The preparation method is totally irrelevant, since it is the actual mechanics of the jutsu which tells us whether or not it'll be effected by the seal. Your logic does not account for why Madara was able to perform the Kuchiyose even after he had died and been summoned via Edo Tensei, only being denied by Naruto (as he's a Jinchuuriki of the 9 tails).
madara still has his contract with the kyubi,when a summoner dies,hs summon is returned back to it's home,as seen with the animal path,but the contract remains,just like the mizukage.
Edo tensei is not an animal summon,the caster dosent make contracts with dead bodies does he? So what's there to seal?. The only weakness is the fact that if anyone edo knew the handseals,they could seperate themselves from the summoner.
And the summoning of edo tensei just summons the coffins and the individuals where he wants them,it has nothing to do with contracts,the people are dead,there is no contract between them and the caster,so there is nothing to be sealed.
The mechanics of edo are nothing like normal summons,in a normal summon,you make a blood contract which can be removed by contract seals, in edo,there is no contract at all,a ritual in which the dna of a person is used to bring him back to life at the expense of another life,then the one brought back can be summoned anywhere the user wishes. You really think a jutsu as powerful as edo tensei will be removed by a contract seal?,cannon shows that it has been used on animal summns only.cannon shows that edo has one weakness,it is cannon that a contract seal hasnt been mentioned even a little as having any effect on edo.
Kabuto learned edo from orochimaru,oro had hashirama and tobirama,what maked you think he didnt have madara?
Kabuto couldnt have gathered the dna all the 7 ninjas of the mist,hanzo,the 2nd mizukage,the fourth kazekage,the third raikage,muu,yoroi,chiyo,dan etc by himself, and certainly not madara,he just enhanced him with the cells of hashi that oro had. He most likely gathered nagato,itachi,deidara,kakuzu,sasori by himself.
Oro most likely had those edos himself,and probably would have used it if hiruzen didnt seal his arms.
If minato somehow gets a contract seal on him,what's to stop him from placing a tetragram seal on minato? As he needs to touch him to do that,minato was known for harashin,not his foot speed,he wasnt really that fast when he fought tobi without harashin and was almosy sucked in. Not to mention oral rebirth if by some unlikely event he us tagged,a new body will just come out,and then he would have figured out his tech by then.
I see oro beating minato,he has no way of hurting oro.