graf_chokolo stated already that he is able to mount the ps3 ufs so partitioning won't be necessary, an image file or bundle would work.
can't imagine that gfx ram as additional memory is an option, read-speed is far too slow, even slower than reading data from harddisk.
Yes, but even asbestos V15 is a somewhat crappy solution and more the like a POC. The kernel is packed besides stage1/2 loaders to asbetos.bin in USRDIR - which seems to be copied to /dev_flash as lv2_kernel.self - so if you want to build your own kernel for your favorite distro (I use gentoo) you have to install all modules to linux.img but also need to build a new asbestos.pkg containing the new kernel, install that etc. Several linux.img's around suffer from the problem of incompatible kernel/module version. IMO graf_chokolo's way is the best to go, simply put improved petitboot to vflash that boots off your kernel that has to be in your linux.img, reading parameters from your kboot.conf