LTCG is still 15% plus state right? Or did the Dems fix that?
interest deductions come off at the top marginal rate assuming you qualify. That's at least 20% plus state. so there's a chance you could make up some of that on taxes.
Unless you're banking on dying without selling the investments. Step up in basis basically wipes out the taxes on the gains assuming you stay under the inheritance tax.
For that type of loan interest deduction would never come into play unless you had a funky tax situation(at least for a married couple.)