IF his parents can commit in a way that will go on and enable him to marry off all his kids. We’re talking trust funds. Otherwise we’re talking about Bitachon on programs…
According to your condition, almost nobody would devote their lives (or even the first several years) to full-time learning.
Trust funds? Bitochon comes in somewhere!
As far as the second point, a serious learner should make sure to marry a woman who shares his goals. But the risk you describe does not and cannot mean that nobody should learn full time.
If Klal Yisroel followed your criteria, we would have no gedolim, c”v.