Braze-ons for fenders and racks are really nice, making it very simple to add or remove them. However, you can work around the lack of braze-ons if the bike is suitable in other respects -- eg, geometry, clearance for larger tires, room for pedaling with panniers, etc. Regarding fenders, SKS makes several types of fenders designed for bikes with no mounts, including their new long version of the Raceblades. Not as good as total coverage fenders, but certainly better than nothing.

Regarding a rear rack, you can install just about any rack with P-clips. The more important issue is whether the bike's chain stays are long enough so your feet won't hit the panniers when pedaling.

The most important issue: Is the Bianchi Celeste green? If so, it might be worth the adaptations. If not, maybe not. (Just kidding.)

That said, the Soma Saga is a great frame for the money and would probably be my choice if buying a touring frame right now. They weren't available when I bought my Bob Jackson several years ago or I probably would have gotten the Soma.