Technically SR3 rules allow for casters and adepts to take cyberware, at the cost of reducing their magic rating by 1 point for each point of essence lost (rounded up, so even 0.01 lost rounds up to 1.0).
Historically it's been avoided on the MUD, as as you guys noticed - it was feared that it would get mages and shamans an edge over other archetypes. But due to the decreased magic rating, it's been discussed again recently - with potential that eventually mages and shamans (and perhaps adepts, though reducing adept power-points would be difficult in MUD mechanics) would be able to install cyberware.
In tabletop, where your character is likely lucky to earn 20 karma over his lifespan - this nerfs co-mingled awakened/cyber right quick. In a MUD environment where we're talking about high-level characters with karma in the 200-300+ range, it's a different story. A mage would technically, under revised mechanics, be able to spend a buttload of karma initiating 3-5 times, then burn those magic rating points in trade for cyber. The effort and time involved to accomplish this, not to mention the karma cost, is roughly on par with dropping all that karma into skills/stats/spell-foci for roughly the same results. Making it a bit of a wash long term. This also brings them up to parity with high end street sams, instead of being ahead of. 300+ karma in stats and skills, and millions of nuyen in best-of-the-line cyber can make for one twinked cybered character.
That said, if you want cyberware now - don't roll a caster. It's a long ways out yet, if ever.