Presonus has excellent StudioLive 3 series 16/24+32 channel mixers, that allow external connection to expansion preamps (up to 64 channels) through ethernet connection, they call AVB.
So a 32 channel StudioLive 3 series mixer with a 16 channel external stage preamp, connected by ethernet cable (AVB) - would give you 48 state of the art, digitally controlled channels of live mixing, with 32 channel SSD recording, color display screen and 32 moving faders.
If you absolutely require 48 faders, linking 2 - StudioLive 3 - 24 channel mixers should perform well.
With your Front Of House mixer near stage, you can run a 48 channel standard audio snake.
If you want to mix further back, you can snake; or 48 channels of external preamps can be additionally purchased and located at stage sending back all signal to the SL3 board over one, ethernet AVB cable.
