I do see many Potential Benefits of Bio-Synthification, but also many Risks.
If Mankind got to the point where Transhumanism were even an actual Issue, it'd have to Ensure that any Cyberization didn't Eliminate Reproductive Capabilities and also didn't put Mankind at any Risk it wouldn't otherwise be Subject to in the Event of a Technological Collapse; Cautions must be taken to Ensure this Technology doesn't fall into the Wrong Hands, of course, as with anything that can be Abused.
I mean, what if it ends up like G.I.T.S.; with Cyberbrain Hacks or the Technological Equivalent of Sclerosis? Even if the latter is Treatable, it does raise new Privacy Concerns; Especially if a Regime could Subpoena your Memories!
Assuming those Legal Issues could be worked out (Good Luck; it'll be Needed!), there's still the Problem of Transhumanists usually looking to Subjugate any who Refuse this.
If even a Minority has this (and it'll likely be a Select, Well-Connected few that could Afford it, at least to start with) that comes to Dominate Society, the very Essence of the Scenario could and likely would Result in the Oppression of those that Refuse it; even if it is not a Concerted Effort, the way those not "Wired In" even today can be Disadvantaged by Society should Indicate how much Worse this would be.
Some have said one or the other should Colonize the Moon or Mars etcetera, but then I've still seen Transhumanists saying that "Outdated" People should be "taken care of"... and look at what "Welfare" has come to mean, Contrary to its Historic Meaning, to see why I don't Approve of this.
Perhaps, if it is to Occur, there should only be Bio-Cyberization as an Option for Adults; no one should be able to Decide for a Child or Teen that it is Acceptable for them, and an Adult's Temperament will Reduce the Likelihood of Regret in one's Decision to do it. If the Process were Reversible, it'd be more Appealing... but I'd still go with the same Restrictions.
While I do like 15 for a Driver's Permit, 16 for a Drivers License, 18 to Vote or Smoke, as well as putting Rental Cars to this Age, instead of 25, as it is in at least some States, and I would set the Age to Purchase Alcohol at 16 (many European Countries have done this and Lowered Alcohol Abuse Rates), I would put the Age for this at least at 25.
Not only must Life be Considered, but also Quality of Life; this Includes a Respect for Human Dignity. Someone, you know, would say "Little Susie could have been saved if it weren't for this outdated law!"; meanwhile, Johnny wakes up to find his Wishes have been Disrespected because he's a Minor and now maybe he Kills himself and/or his Family for this Betrayal. While it makes for Excellent Fiction, it makes for a Horrible Reality.
To Avoid any Problems with Epigenetics (the Semi-Malleable Aspect of Genetics), those who Wish to both Procreate and Cyberize should do the former before the latter.
If it's done in a way where the Biology and the Cyberization are Inherently Fused, at which Point the Subject would be - by Definition - Inhuman, then this would make it all the more Vital that Procreation would Occur BEFORE Cyberization.
If Nanites are used, this is another Case of it being Simultaneously Cool and Disturbing; apart from what could Happen if these Malfunction in other ways, look up "Grey Goo". Perhaps if these aren't Replicating, that last Aspect of it won't be a Concern.
Of course, those Born into a World of Cyberization will have more Encouragement to Cyberize than one not. Since this isn't Natural, and isn't Necessary to Our Survival, it should only be Considered if both the Technical Aspects and Legality can be Worked-Out to the Satisfaction of both Transhumanists and Naturalists; what does not Harm Us as a Race, is up for Consideration. Not everything that Works for one Person or Culture will for another, however; We must look to Common Values, and then Operate within Our Own Cultures towards this Goal. It's not about just any one Generation; it's about all Generations, both Past, Present and Future.
Especially as Transhumanists have Expressed a Desire to Subjugate Naturalists, one must ask if these "Bionics" should be Raising Children at all.
One wonders what the Family Dynamic would be like if one Parent was a Bionic and one Natural; the Child should be Natural, as said before. How much Influence would the Decision of one Parent have on the Child? The more Stable the Family Relationship is, the Less Problems this is Likely to Cause. Still, even in a Best Case Scenario, it seems Impractical.