That's an excellent point. Even if Oswald had gone to trial and been found not guilty beyond any reasonable doubt, that is not proof of anyone else having done it. And, as the OJS trial showed, skilled defense lawyers can insert that doubt. And one of the best ways to get the accused off is to get the prosecution to underestimate them. If you want my opinion-- or if you don't, I'll still give it-- I think OJ Simpson is guilty and that LH Oswald is guilty. In neither case does that necessarily say they had no accomplice or they weren't coerced or tricked into their crimes or their actions suggesting it.
If Oswald "had to be eliminated at all costs," how then is it that Ruby didn't have to be eliminated at all costs? If they-- "those that initiated the killing of Kennedy--" were afraid Oswald would talk because he knew what had happened, the same would be true for Ruby. And for whoever took Ruby out. [Ruby lived 3 years in prison and died of lung cancer.] As for Ruby having access to the Dallas police basement, he was well-known to have reciprocated with the Dallas police-- he arranged liquor, hookers, et al, for them and they largely left him alone to run his strip clubs, in which he was high-tempered and physically threw undesirable patrons out, while taking care of his 'girls.' Is he the only such entrepreneur in vices who had such police acquaintance? And considering, for the day, that you could walk into an airport boarding area with no patdown, xray, or even questions, it wouldn't be that hard to take a gun almost anywhere, especially if you had reciprocating acquaintances.