To give my answer to the OP.
If I understood Solas's motivations correctly, I would go through with the plan to break down the veil.
In the entire play through's of the DA series, it is apparent that there are many aspects of Thedas that have gone haywire which was not intended to happen.
(1) The death of Mythal by the hands of fellow Evanuris which triggers the event of the veil being brought up in attempt to seal away those that would try do to even greater harm to the world including the ancient elves
(2) The treatment of the Elven people throughout history after the veil went up. But it isn't just them it is a major factor though
(3) The Spirits becoming demons when entering the physical world since the veil went up. They are no longer what they once were.
(a) Mostly due to people fearing them. They (the people) were taught to fear and deny which lead to the spirit to become a demon in the physical world.
(b ) Those that summon a spirit with little knowledge (thanks to continues wars, slavery etc erasing former knowledge) denying the spirits purpose wrapping it into a demon
(4) The Blight, to me the blight is a manifestation in physical form of resentment, hate, rage, greed.
(5) The Taint caused by the blight is infection it even affected Lyrium (a source of power) but in a sense it is also alive
(6) The Tranquil people cut off from the fade, but more so evident that it is the world cut off from it due to the veil.
These are the following six points I think Solas see's that need to be corrected even if it costs many lives. He feels guilty that his action in making the veil has caused so many to suffer not just the elves, but the world and the spirits. The world cut off from guidance of the spirits that walk along side them back then, the whole spiritual connection to the world. But in the same breath, Solas if he has a good connection with the Inquisitor is secretly hopping that he would be stopped, to be shown there is another way a glimmer of hope. Solas blinded by his guilt has not seen another option aside from forcefully taking down the veil.
However since I am not Solas, my inquisitor would do her best to stop him from doing such. Adding more death is not the way. I would hope in the future of DA series that we have the choice to not to kill him. But I understand that if death is the only thing that will save him then so be it.
So sorry about the long post, I am bit tired