According to datasheet SJEP exhibits somewhat different behaviour compared to SJDP, so I suppose that something can be done towards your idea (although I don't know what your present, working, schematics looks like).If there is a benefit in using the Schade approach (needs to be confirmed), it should be done with composite device (low power JFET at input plus SJEP, both locked in the Schade loop) because big parasitic capacitance of SJEP will force us to use small value resistors in the local feedback which leads to small Rin, etc...Anyhow, there is some work needed to asses the problem and to evaluate possible solutions. Right now I don't have neither SJEPs, nor the time to play with them...