I always thought paid maternity leave should be handled thusly...
In Australia, regardless of who you work for, you accrue superannuation benefits (which I beleive is known as 401k in the US). These managed funds are handled by many different private companies and are generally transferrable from one company to the next. This is basically your retirement money. You're allowed to put in extra if you like from your post-tax income, and depending on your employer, you can even put some of your pre-tax income in there, resulting in lower take-home pay, but also less tax.
To get around the whole unfairness of who has to fund maternity leave (ie, current employer or federal government), I think a parallel system should be set up so that those who might think they will need maternity/paternity/parental/carers leave at some time in the future can fund it themselves. They would then put aside a small amount from each pay (pre or post tax, depending on what deals could be arranged), which goes into a superannuation-like managed fund that can grow over time.
That way, if a woman decides to have children and wants to take time off work, she can draw upon these funds for general living expenses while she isn't working.
This has the advantage of it not being any one particular employer's responsibility to fund, nor the governments, and if the "maternity leave fund" doesn't get used (ie, hasn't been touched by the time the woman reaches menopause or whatever) it can be cashed in or transfered into the normal superannuation fund.
Another advantage is that this approach would eliminate scammers who would abuse mandatory maternity leave schemes (ie, working at a place just long enough to get maternity leave and then getting pregnant and taking full advantage of it). What you can get is equivalent to how hard you worked - not some manatory minimum that applies to everyone, regardless of how long (or little) they have worked for the company and whether this is their first or fifth time.
This would be available to men as well, incase they think at some stage in the future they would like to take paid paternity leave (also to stop the feminists bitching about it all being the woman's responsibility, yada yada yada).
Should paid maternity leave ever become a reality in this country, my proposal would solve the funding of it.
As for the issue of having to keep a job open, thats another one altogether...