It only takes soldering a jumper wire from the tone pot wiper lug that is the input to the Phat II, to the tip lug of the jack, bypassing the Phat II, and taking the battery out. Easy and reversible: just clip it out if you don't like it. Only after you have done it, or after using an alligator clip jumper to see what it sounds like to you, can you make that determination. I'm not trying to be a smart-a$$. "Should" is a subjective word. If you like straight ahead bass tones, and you don't mind modifying an instrument, especially a bass as common and inexpensive as the Ibby SRA/GR series, then go for it. If you are unsure about your skills with a soldering iron, or don't think it is cost effective to have someone else do it, or are concerned about selling the bass later, then maybe not. I decided I liked my bass with the Phat II and kept it. But then again, I have modified every instrument I have owned in the almost forty years I have played electric guitar and bass, even my Rickenbacker 4002 bass.
I would say that most of the problems with noise and hum with P/J configuration SRA/GR series basses are as a result of the J-single coil bridge pickup being just that - single coil instead of humbucking. Since the Phat II also boosts highs as well as lows, any inherent noise will be more apparent when the Phat II is engaged. And the Ibanez SRA and GR series basses are so inexpensive it is not necessarily cost effective to upgrade the pickups or add additional shielding, although a split coil J-bridge pickup would be a great improvement to eliminate noise and hum. On my SRA305, I did upgrade from the stock EMG Hz40's (very good humbucking passive pickups in their own right) to EMG active soapbars and the EXB, which is exactly the same control as the Ibanez Phat II, just with the Ibanez proprietary name etching on them, (The older ones actually say EMG on them!) and only because I wanted the full insulated treatment (plastic covers, no bridge ground) for outdoor gigs, and I play nylon tapewounds. Because for me, it is a tool to earn money, it was worth it, even though the cost of the two EMG soapbars and the EXB ended up costing almost as much as what I paid for the bass originally as a factory second - the control panel had been opened up to fix something, breaking the little tape "seal" on one of the back cover screws, so the retailer could not sell it as "new," although it had never been out of the store.
So with all the information I can supply you, "should" you modify your instrument? If the answer to everything I have stated is, "Yes," then probably. All I can do is post information, not guarantee results, which seems to be the tone of your original question - asking for a guarantee of suitability of jumpering the Phat II.
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