I very much doubt that Van Aert will be able to do that, even top10 seems difficult taking into account that he only raced once this season, I would say that Alaphilippe has a clearly better chance of beating the two Tour winners and the rest of the GC field.
However I expect a great battle in the hilly stages between Van Aert, Alaphilippe and Van der Poel.
I also doubt van Aert is going home with the win, but i do think it's really not far fetched for him to end up in the top 10. I would actually put a pretty penny on him doing so. Keep in mind this isn't the TDF and quite a few of those guys aren't in prime shape nor motivated, while van Aert, getting ready for the classics and coming off the Teide, is likely closer to prime shape than the likes of Majka or Nibali. Add to that the ITT where he can take 30s and more on all GC favorites except Pogacar, Almeida and Alaphilippe. Add some boni seconds as well, and the fact that half of the GC climbers could get caught out in the hilly stages if raced hard, and Majka, Landa, Pinot, Bardet... could very well have to finish more than 2 minutes ahead of him on the MTF in order to finish ahead of him in GC.
No, i can't imagine him going home the winner, but i can certainly see him in the top 10 maybe even higher than one would think.