i3 downgrade for improved battery life or... I wouldn't bother as the i7 won't offer much over the i5 parts. If only a Quad would work...
2570P uses a socketted CPU just like a 2560P so can be user upgrade to faster CPUs. Now just be aware that any faster CPUs not listed in the Maintenance and Service Guide or on HP's options will likely cause warranty issues or even void the warranty.
A 35W i7-3612QM (quad) is a drop in replacement for a 35W i5/i7 dual-core CPU so no problems in it working. A 45W quad works fine in a 2560P and a 2570P chassis looks identical so no reason it won't. In fact we find there's a 2570P with a i7-3720QM being sold in China. See details.
The socketted CPU gives a HP 2560P/2570P an upgrade path. A unique feature considering other thin-and-light ultrabooks and ultraportables such as a Lenovo X220/X230/T420s/T430s, Dell E6220/E6320 and Toshiba R830/R940/R840/T840 all have soldered CPUs so have no CPU upgrade option.
I should add that HP disabled RAID-0 capability on the 2560P when the chipset is perfectly capable of doing it. I'm not sure if that's been changed in the 2570P. I'd guess not. I figure RAID-0 could be added if someone was willing to flash the 8460P bios on their 2560P by using an eeprom burner.
If HP they enabled RAID-0 (2.5" drive bay + upgrade bay) then the combo of i7-quad CPU capability and RAID-0 would make the 2570P the smallest, most powerful system available.
At the moment that honour would go to the 13" Sony SVZ (Z3). It has RAID-0 and i7-3610QM (low end quad), in the chassis the size of an ultrabook.
Some very minor tweaks to the 2560P/2570P (RAID-0, official 45W i7-quad support, IPS panel, mSATA support) and 2170P (hi-po 6/9-cell, mSATA support, IPS panel) could generate a lot more interest in those system.
Lenovo certainly are keeping tabs on discussion on this board of desirable features and integrating them. HP have missed the boat for three generations now (2540P, 2560P, 2570P). I can understand why Lenovo is gobbling up HP market share.