Integrated or an expression input? Playing around with my Lex, I assigned the expression pedal to the drive control and kind of liking being able to use the pedal to go from clean to really dirty . . .
Every dirt pedal under the sun can do this.
Simply stick a volume pedal in front of it. The volume pedal will increase or decrease the the resistance of the signal hitting your pedal, and thus, pregain.
Or better yet, just use the volume control on that there gee-tar of yours. It's kinda what it's for!
Then you need JFET dirt pedals.
They are perfect for cleaning up on the volume knob/pedal and not turning down in volume. Very amplike in that regard and substituted for tubes in lots of amp-in-a-box emulating pedals.
Check out Menatone, Catalinbread, Okko, Himmelstrutz etc...
Or Kingsley, who use high voltage tube circuits that clean up like amps do...cos they are tube preamps in pedal form.
Zero volume loss when backing off the volume control.