Don't know if this would apply to you guys, but we actually broke our boom by cracking it from tightening the main sheet too much at anchor
. We had no idea it was cracking there, at the hard vang attachment, till there was a fairly severe wind
puff from the wrong direction, At that point, having a topping lift available there, to support the aft end of the boom while we dealt with things, would have been a big help. It was obvious from the break that it had been working up to it, unseen, from the inside out. The boom is sistered there, too, so it HAD been reinforced.
There are other occasions, also, when we have used the main halyard to take the weight of boom and sail, while repairing at the gooseneck. Or for mending the boom. So, I'm all in favor of having the boom topping lift, operable from on deck
, though (so the OP'd have to install a block and run a line all the way).