All 360's are hackable, exception of Xenon and Winchester (Xenon being shite, not worth the time nor money and Winchester being actually unhackable.
It doesn't really matter which one you pick altho preferences would go to Slims for their build quality, Phatties are simply more unreliable.
I'd say get a Slim, crack it open and identify the motherboard.
After that, you can make your selection of chips.
If you want a simple install, I'd say grab a Glossy Slim 360, they should all have Trinity motherboards which are fairly simple to solder chips in.
Upside is that you only need a glitch chip (CR3 XL/CR4 XL or AceV3) and the TX DemoN.
I'd go for a full TX setup, their hardware is superb.
I'm running a first gen coolrunner on RGH1 in me Falcon, instaboot to 1 glitch cycle on nowadays shitty wiring routes ;p