I would imagine that the best way to manage an amplified instrument in a pub session environment is to face the speaker at the player of the instrument and set the ground rule that those playing such instruments should be able to hear any other instruments being played as well as the amplified sound of their own instrument.
The reflected sound from the pub wall behind the player would enable the rest of the room to hear the amp, the added bonus is that if it gets too loud then someone sitting close by would notice and be able to adjust the volume.
But surely the whole point of a session is to create a good communal sound and not be louder than everybody else, if you can't hear the instrument across the other side of the room for the sound of you own then you are being too loud.
As for amplifiers, there are loads of small almost pocket sized amps out there that would create enough sound for a session environment and they are relatively inexpensive.
Any instrument ought to be playable at social volume if you want to play it load, join a rock band or go to an open mic session, there are a lot of each knocking about.
By the way Burton Coggles I really enjoyed what you did with your electric lap slide guitar over my acoustic version of Little Red Rooster (YouTube: here )