Good rundown of the tradeoffs! When I was VP Public Affairs for E’Prime Aerospace, we were serious about using Ascension Island. E’Prime had permission to commercialize the MX missile (aka LGM-118 Peacekeeper), which was designed to be transported with minimal operational costs, so a military transport jet to the existing landing strip at Ascension Island would likely have been feasible. The launch site would have been a cliff where an overhang would have permitted the launch of a two-side-boosters configuration’s exhaust to be deflected.
However that was just after I’d been Chair of a grassroots coalition to pass the Launch Services Purchase Act of 1990 against the opposition of “The Big 3” (plus Orbital & NASA), and there were some dirty tricks played to scare our investors away (most prominently a “coincidental” announcement of the Delta Clipper program the very day we were meeting with investors in Long Beach*). That, plus the lack of the kind of capital shaken loose from Wall Street by the DotCon era doomed several otherwise viable launch companies of that era.
*There are more “coincidences” to that story that would scare the hell out of anyone who thinks that the government is there to help you. This was very clearly a targeted attack on a private launch service company by a criminal conspiracy within the MIC.