to rule it out simply on the basis that "well, it didnt work in the 80's" seems like it should be better qualified to me.
Lack of access to LHR and being stuck at LGW helped to kill off Laker, prevented BCal from challenging BA and allowed BA to swallow them up and nearly killed off VS. Read a couple of the biographies of SRB and this point is crystal clear, if they'd remained at LGW, they would not have survived.
As to working in the 80s, it didn't work under a decade ago when BA last tried it. Indeed Delta hung on at LGW until very recently but even they quit in April of this year. The only US long haul at LGW is US on LGW-CLT which I understand is mainly LGW-CLT-MCO leisure focussed so is a good fit for the LGW demographic. Indeed BA are adding LGW-LAS this year in addition to LHR.
Some things so work and work well at LGW, the trick is knowing what they are and sticking to them.
You cannot lead a market to where it won't go. I have seen nothing to change my opinion of this, recent long haul has seen Air Hong Kong come and go in six months and Korean and Air China play the waiting game until a suitable LHR slot opens up.