It seems to me that both the view of the Restrainer being the Holy Spirit or the Church is impossible. Reason being is that scripture seems to leave the warfare that takes place in the heavenlies to the Host of Heaven. Ephesians 6 re-reminds us that this warring continues to go on.
Then said he unto me, Fear not, Daniel: for from the first day that thou didst set thine heart to understand, and to chasten thyself before thy God, thy words were heard, and I am come for thy words. But the prince of the kingdom of Persia withstood me one and twenty days: but, lo, Michael, one of the chief princes, came to help me; and I remained there with the kings of Persia. Now I am come to make thee understand what shall befall thy people in the latter days: for yet the vision is for many days. (Daniel 10:12-14)
This is a familiar case, but I think it may shed light on the topic as it deals with the latter times.
Then he said, "Do you understand why I came to you? But I shall now return to fight against the prince of Persia; so I am going forth, and behold, the prince of Greece is about to come. "However, I will tell you what is inscribed in the writing of truth. Yet there is no one who [u]stands firmly[/u] with me against these forces except Michael your prince.
The reason why it seems to me that Michael fits 'better' is that [i]The Man of Sin[/i] appears to be a leader that will lead the world as if he were God Himself. The nature of the fighting in Daniel's times was with these 'princes' of nations. What do these princes do? They jostle and fight for power. This is serious warfare. It is a very real warfare also. There are hints of its goings on all over the scriptures. When Michael disputed about the body of Moses or when the angel smote Herod in Acts 12:23. When the Host of Heaven appeared II Kings 6:
Therefore sent he thither horses, and chariots, and a great host; and they came by night, and compassed the city about. And when the servant of the man of God was risen early, and gone forth, behold, a host with horses and chariots was round about the city. And his servant said unto him: 'Alas, my master! how shall we do?' And he answered: 'Fear not: for they that are with us are more than they that are with them.' And Elisha prayed, and said: 'LORD, I pray Thee, open his eyes, that he may see.' And the LORD opened the eyes of the young man; and he saw; and, behold, the mountain was full of horses and chariots of fire round about Elisha.
I don't have the mind power to put it all together, and I'm not about ready to go out in left field, but it seems to me that what is being 'restrained' is Satan and his bunch and that the 'restrainer' is Michael. That is not to undermine the working of the Holy Spirit or the Church; but God seems to have an order to these things. I have often thought that Satan will be cast out of Heaven and into the earth at some point. For now his carryings on take place in the heavenlies. But at some point he will be cast into the earth. And from earth he will be cast into the bottomless pit and from the bottomless pit into the lake of fire.
Satan is on a downhill slope. Since he said he would ascend into the Mountain of God and God said he would cast him into the sides of the pit- he has been going down! down! down!. Pride goes before destruction and fall. He is cast from the presence of God (3rd Heaven) and then cast from there into the 'heavenly realms' (Eph 6). From the heavenlies into the earth (Revelation 12:7-10). This would appear to me to be the point in which the Antichrist is revealed. He is then bound with a chain in Revelation 20 for 1000 years (whatever that means) and then 'loosed for a season'. From there fire from God comes down to destroy those deceived and the Devil goes into his final judgment to fulfill Isaiah 14:
5 The LORD hath broken the staff of the wicked, and the sceptre of the rulers. [u]He who smote the people in wrath with a continual stroke, he that ruled the nations in anger, is persecuted, and none hindereth.[/u] The whole earth is at rest, and is quiet: they break forth into singing. Yea, the fir trees rejoice at thee, and the cedars of Lebanon, saying, Since thou art laid down, no feller is come up against us. Hell from beneath is moved for thee to meet thee at thy coming: it stirreth up the dead for thee, even all the chief ones of the earth; it hath raised up from their thrones all the kings of the nations. All they shall speak and say unto thee, [u]Art thou also become weak as we? art thou become like unto us?[/u] Thy pomp is brought down to the grave, and the noise of thy viols: the worm is spread under thee, and the worms cover thee. How art thou fallen from heaven, O Lucifer, son of the morning! how art thou cut down to the ground, which didst weaken the nations! For thou hast said in thine heart, I will ascend into heaven, I will exalt my throne above the stars of God: I will sit also upon the mount of the congregation, in the sides of the north: I will ascend above the heights of the clouds; I will be like the most High. [u]Yet thou shalt be brought down to hell, to the sides of the pit.[/u] They that see thee shall narrowly look upon thee, and consider thee, saying, Is this the man that made the earth to tremble, that did shake kingdoms;