Earlier quoted context omitted.
It looks like all the isotopes of LI are very short lived. Is the problem some of the daughters, or perhaps the Fe and C in the steel that are the problem? https://www.thoughtco.com/lithium-isotopes-radioactive-decay...
Yes, the problem is the steel.
Making the blanket out of molten metal would be a problem anyway because it is conductive, and you are trying to control a magnetic field inside the reactor chamber with coils around the outside of the blanket. Varying magnetic fields would set up eddy currents in the metal that would oppose changes to the field. So you probably need a diamagnetic insulating compound of lithium. What to bind to the lithium is a tricky question, because you don't want it stealing neutrons you need to breed tritium from, and getting radioactivated besides.
Under ideal conditions, if you had pure 6Li and 7Li, a neutron it stops would end up producing more than one tritium nucleus. The problem is that you have a great deal of other stuff that will steal neutrons, including pipes.
You could make the blanket with LiD, lithium deuteride, and any neutrons the deuterium picked up would make a tritium. But lithium deuteride melts up around 700C, which is hotter than most people like to imagine operating reactors. Worse, you cannot chemically distinguish the deuterium from the tritium, when you try to extract it.
There is a separate problem of extracting any bred tritium, in parts-per-billion concentration, out of the blanket.