I agree that third party options are probably the only option. What I plan to do as a primary workaround is not to rely on the Verizon international SMS system, but as a secondary, to follow a route as you suggest. It does appear to be a pain though, as some of these outfits seem sketchy and one would have to write down the number and reinput it from the website, etc.
When a Verizon customer roams overseas on GSM systems, it is my understanding that the carrier that is used is Vodaphone. Hopefully, they don't have the same problems, so while overseas, it may be that the texting works OK. I will have to see when I am there. Perhaps someone else has tried this can can advise?