Whats that saying - necessity is the mother of invention.
Theres your chance to invent something and possibly make some money
If it was me, and I needed to force a tip to fit, I would do exactly that, whip up an adapter sleeve on my lathe... Yeah making your own is not for everyone and I doubt there is really a market for it in the end, but it's an option none the less...
Presumably the RJ45 jack was soldered into place. How was it done?
Magic...
But a valid question, if it was reflowed it can handle the heat necessary to reflow again for removal, if it was wave soldered then removing from the underside is certainly a valid option, and if it was hand placed/soldered reverse those steps...
Once again I'm going to chalk this up to a lack of hands on experience, technique and procedure necessary to accomplish the job...