Bluetooth Wireless Sensor Network

Can I use bluetooth technology (which is point to point connection) to build Wireless Sensor Network (which is point to multipoint, or mesh network)?

You seem to have already explained to yourself why this is a bad idea. You can do it, but ESP8266 or NRF24s are a better idea, as they are made for this sort of thing.

Is there any way to modify the point-to-point into point-to-multipoint using Arduino+software? This is what I am asking.
Something like this:

but with bluetooth modules.

Thank you.

You would have to configure a base station to auto-connect to others on a rotating basis. The best reason for doing this is that you already bought the blueteeth by mistake, and you can't afford NRF24s @ $3 each. Don't even think about a mesh network.

http://www.martyncurrey.com/connecting-2-arduinos-by-bluetooth-using-a-hc-05-and-a-hc-06-pair-bind-and-link/

You may find a BLE module is a better choice, but still a bad idea.