Does this cellulose-insulation blow-in product for the end bits of the attic look good?

[Garald]

So, the contractor is willing to use cellulose-based insulation instead of rock-wool for the blow-in insulation of the combles perdus (the low-height end bits of the attic).

 

1. Does this product look all right? It's what the contractor proposes.

 

https://www.soprema.fr/fr/product/isolation/toiture/toiture-en-pente/combles-perdus/univercell

 

2. The contractor and the architect assure me that I can view this as an investment, in that it won't be lost even if I raise the roof (provided I raise it following the lower red line in the diagram below; in the other two possibilities, we would not really be talking of roof-raising but of building an extra story). Does this make sense? (I suppose it will be lost if I follow one of the two other possibilities?)

 

[Garald]

PS. The contractor proposes to do this for 3250eur+taxes (whether it's cellulose or rock-wool). Does this sound like it's in the right general ball park? The house is about 12m long (on the inside).