If a laminate is affected by osmosis it can't be repaired in the way that you can't change the laminate properties. But you can definitely take one of the causes away: the moisture. This can only be done durable, and with a lifetime warranty, by laminating a few layers of glass/epoxy or glass/vinylester over a well dried laminate. I would only advice coatings as gelshield for boats that might be sensitive to osmosis, for instance if sisterships have developed blisters. I wouldn't dare to use it to repair a boat, in the way as to give a guarantee on it. Some yards do, but only very limited.
Most of the time osmosis isn't very damaging, a wet resin matrix loses some strength, but that's what the glass part in the laminate if for anyway, and a wet laminate doesn't have to have osmosis or be susceptible to it(most boats are wet to some degree). Osmosis will cause some minor delamination, affecting the panel stiffness, but that's only a very small part of what gives stiffness to the whole structure. And osmosis usually forms in badly degassed, thus porous laminates, which already have less panel stiffness.
So yeah, it's not very pretty, and bad craftsmanship from the builder. But every boat has its secrets, no boat is perfect. It wouldn't be a big deal for me personally. So here, another opinion for in the can of worms