NRF24 CE and CSN connections without I/O pins easily accessible I want 2 Arduinos communicating to each other, but only in one direction.  Arduino A = tx  and Arduino B = rx.

I have this working fine connecting CE and CSN on each NRF24 to pins 4 and 5 on each Arduino and using the nRF24L01 library.  No problem.

Since Arduino A will always ONLY be transmitting and Arduino B will always ONLY be receiving, can I do this with CE and CSN instead:

Arduino A --- put CSN to GND  and put CE to 3.3V
Arduino B --- put CSN to 3.3V and put CE to 3.3V

As to why?  This would simply help me interface the NFR24 to existing custom PCB's I've made which have no easy access to I/O pins.  My PCB's do have easy access to MISO, MOSI, and SCK.
No, you really do need the CE pin for both TX and RX modes.  See the following excerpts from the nRF24L01 datasheet.  They work practically the same for nRF24L01+: