But even if the studio or a fan can capture the atmosphere and tension that Miura provided us, wouldn't be fair to give them chance, even if we know that it won't be the same type of writing quality as the Manga?
Hmm, there's several things here. First, you're assuming someone can capture the "atmosphere and tension" of Berserk. That's a big assumption. How are these even defined? Different parts of the story have different atmospheres and tensions. For example, the mood is pretty relaxed on the island as of episode 363, but with an underlying current of uncertainty about the future, and a vague feeling that tranquility won't last forever. Very different atmosphere from when the group ventures into the Qliphoth in volume 25, when Guts and Casca talk about the Bonfire of Dreams, or when Guts is rushing to get to her in volume 19. And this can change on a page to page basis, too. Sticking with episode 363, it starts with a very melancholic scene between the Skull Knight and Danan, then moves on to a funny scene between Isidro and the witches, and ends on a mysterious note, with the boy appearing in front of Guts.
Second, in your hypothetical scenario, that would be achieved even though the writing quality wouldn't be on Miura's level. I'm not convinced that's possible. Berserk is unique in many regards, including the fact it has continuously evolved over the years. You never see the same situations and fights, and characters constantly evolve as they experience things. What this means is that you can't just keep things "the way they are". The characters have to keep developing as they are faced with new ordeals and dilemmas. Miura did it so well that we never quite noticed them changing, just knew that they had. It always felt natural yet was done very subtly and in an economical manner, without being detrimental to the action. This is exceedingly important, because if the characters don't feel right, "atmosphere and tension" are meaningless.
Third, there's the fact Berserk is told in a visual medium. Most of the time Miura shows rather than tells. This is central to the appeal of the story. I don't think it could really be Berserk without the biggest moments being told through drawings rather than words. And of course, that means coming up with those big moments, and doing so in a manner that naturally allows for and integrates the character development mentioned above, all the while bringing the story to its conclusion neither too quickly nor too slowly. Berserk is defined by how densely packed each of its pages is while it stays riveting to read. It's a delicate balance, less easy to attain than one might think.
Lastly, you mention fairness. Do we owe it to anyone to let them get a "fair shot" at continuing Berserk? I don't particularly think so, no. Personally, I believe we shouldn't even be having this conversation yet, just out of decency towards Miura sensei. I'm also convinced that someone who would feel entitled to writing Berserk's continuation just like that would innately show themselves to be unqualified to do it.