It's exactly what i've used NIM for !
Indeed, you can configure your NIM server ( after having correctly adding your AIX boxes with your NIM interface ) in order to accept a mksysb installation ; the main mksysb it's not important for the client's specific configurations files : SPOT ressource plays this role
But be careful of what are you doing :
+ First, check your hardware platform with <color blue>#bootinfo -p</color> and modify if it's necessary your NIM config for these platform
+ Create a bosinst_data ressource to control your installation ( i mean in your case to check your RECOVER_DEVICES stanza at <color red>yes</color> )
+ The target disk is important : indeed, it's important to distinguish data and system files, particulary in your case ; it's very difficult to prevents NIM from overwriting some files on a physical disk, so if you have local datas ( .model i mean, but maybe have you a filer or a SAN ), i advise you to create two volume groups (rootvg and datavg for example) and fix the size and location of your rootvg on the physical disk.
Then you can export the datavg before starting a NIM installation, and when it finishs you import it and greatfully you can see your so nice .models ...
Note : If you want to be sure to use your datas again, it's more careful to have two physical disks for each volume group
Good luck altivario, - NIM is not hard, but it's simple to spend a lot of time on it ;-) "Unix, it's like French : nothing is impossible"