Hello Dipankar,
                      As long as you ensure the bulk-source junction doesnt cross the Potential Barrier voltage of the p-n jnxn, You can use Fwd Body-Bias to reduce Vt.....
    But keep in mind,
1.  there's a limit to which you can reduce Vt using this technique....
2.  You would need Triple-Well technology -- costly.
3.  You have to ensure that across PVT, your bulk-source jnxn doesnt become forward-biased.
4.  keep you bulk-source bias programmable to again bring back Vt to normal values while in Power-Down Stage otherwise leakage current can increase.
5.  Ensure your models are reliable when you are using these kind of risky techniques...

I provided you the advantages & disadvantages....Weigh the pros & cons yourself & then decide.

--mayank