Unsure about my structural engineer, can you check his drawing?
There isn't enough information in that sketch to verify calculations (for instance, we have no idea what's on the floor above), but here are some reactions:


Removing 60cm of support may be significant, depending on how much load that wall was carrying.
If the arch is structural, removing it requires additional support.
Your existing building may not be structurally adequate. If you're making changes to those supports, you are probably obligated to bring that portion of the structure up-to-code.
The structure is of no use if there's not an adequate foundation to support it. Your drawing doesn't show any information about the existing foundation, but shrinking the supports from walls to piers may concentrate the load beyond what the existing footings (if any) can support.


I agree with @longneck, you should talk to your engineer about your concerns. There may be ways to avoid some/all of these tradeoffs, or maybe you decide that it's not worth the effort.