If your talking about a stripped down system for use on older Macs,yes it would be a good idea. But you'll never see it happen.Apple wants you to keep buying the latest and greatest to keep the money rolling in!
You can minimize a bit the things in your system.
Like remove the unneeded localizations (DeLocalizer.. at least I've used it in the past, should still work with the new systems). That will give you back a few GB (until the next system update).
Or not install some of the big bulky software you don't need.
Or not install all the printer software if you only have one printer.
And some small tweaks like disabling Dashboard if you don't use it can save the processing power too for the more relevant tasks. Dashboard at least on earlier systems was about 2-5 % of the processor over time, so with a bit lower system it can also help. When I need(ed) disabling/enabling Dashboard, I use(d) OnyX for it.
And having enough clear space on your hard drive is relevant. If the empty space gets to under 15%, the system will be slower (no matter what processor or how big a HD).
I am trying to figure out what you mean. Do you mean a Mac Pro or a professional using a Mac?
As a 2008 Dual mac Pro it has been more than enough for me. Over the years I installed four 1 TB drives in it, a ATI 5870, a USB3 card and an eSATA card to it for some external hard drives (for video storage to share with my media center 2010 Mac Mini).
You should see Handbrakego with all the cores, it uses all 8 cores.