Which tricks were you considering for the 5E3? These would appear to be substantially different amps. A 5E3 can cover a lot of territory, I'd be concerned about reducing it's versatility.
In short the amp has a volume control following the input triode, a Baxendall tone stack between the 2nd & 3rd triodes, then a cathodyne PI (assuming we are excluding the reverb). You don't have enough triodes to clone this preamp. Converting to fixed bias, or incorporating the Kelly NFB loop would seem quite feasible?