Interesting question. I've run D8K's with 4bbl rippers in rock, frost and what have you, same D8K with a Fleco or similar mfr root rake, after the buncher feller and tub grinder in thickly wooded areas. This was after the majority of the stumps were pulled. For that task, you can cover quite a bit of ground that way.
In theory, rippers, root rakes are similar, there is no doubt if one was to properly fabricate one, (strong enough, braced or stiffened and similar) using appropriate materials, may not be good for ripping rock but should work well for root raking, basically what you want, and to scarify the driveway, should work fine. You make those shanks and teeth too long and try and really sink it in, that could present some problems, but it sounds theres no real need for that.
A multi or single shank ripper on the back like the parallelogram style on the 8K's really had some down pressure and force, meant for heavy ripping, really something to marvel at remembering the power combined with the weight.
I do not think the rear mount ripper would be all that great for root raking as its going to eventually trap roots and similar things under it, you'll have to clear it before it gets too high, hence the front mount being more desirable.
Single shank on the front, going to take a lot longer, more run time, undercarriage wear. I think you may be happier with some sort of stout rake fabricated for the purpose. Given the forces at work, you may want to look at similar attachments for fabrication ideas, strengthening, stiffening, could still bend or deform some too. I've seen a lot of home built ones, very useful when needed.
Assuming the push arms, blade, trunions and track frames are certainly built for the dozer blade, a front rake ought to be within what the crawler can handle, but I'd not want to create something too aggressive or really put the power to it, meaning not overdoing it. I'd vote for the front mount rake, probably take some time, but worth it, take a look at Fleco, and or heavy duty multishank rippers to get some ideas. The one we had on the 8K was very productive in the sandier top soils in NJ. Large rocks are probably the worst enemy of these, more so with a home built one if not reinforced enough, but with light to moderate penetration in cleaner soils they sure sort out those roots, we would next bring in the scrapers to strip topsoil, still needed screening but was not bad once the root rake was run through it.