for 10 hull with 3.5BN you will be looking at a Frigate type. (and not a very big one at that)
This will be smaller and less capable (but still a worthwhile thing to design
).
I have done a quick cut and paste using your ships of what sort of size I think it might be (and I may be wrong
if you use it sorry but you will have to redo the hull better than I have).
A FF (frigate) will not have any duplicate weapons (it just cant afford them, the duplication is having 10 hull for the price of 2 DDs).
You may have to cut your systems (weapons/radar to budget).
JSB
If you have $350m then you might look at, (these are just from the internet so probably a bit wrong)
- Danish Absalon: 269 $ million.
- Danish Iver-Huitfeldt: 332 $ million.
- South African Valour Meko 200A: 327 $ million
- German Braunschweig K-130 :$309 million
- Turkish Milgem : $250 million
- Malaysian Kedah : $300 million
- Omani Khareef : $262 million
Defiantly FF or Corvettes