Simon,
Please don't let the worry of the outriggers (which as you correctly state, aren't really 'outriggers' at all, but sill strengthening structures, but that is what they appear to have now been accepted to be called by us lot!!) put you off too much...
...it's just the latest scare/worry amongst a paranoid group of people (of which I am a fully paid-up member) looking for the next project
As with any car, as the elan is getting older, different things are discovered which will need looking at/addressing. If you liken it to the human body it may be thinking something like this:-
500 years ago people didn't seem to suffer from many of the diseases/conditions which now plague us - not because they didn't/couldn't exist, but simply because the sufferer would die defore they became an issue. As society discovers a way to deal with each deadly illness, life expectancy increases, so a different condition gets the chance to emerge. When an average male was only expected to live until they were 45 years old, very few suffered from dementia, cancer or other such (more common, but now being investigated/treated) ailments... at that time you would get an infection and die. (unless you were killed in battle). Once antibiotics came along, and warfare changed, so life expectancy changed and other things eventually caused us to pass on - so it is with cars.
There will always be a 'new' car-killer to emerge - until someone finds a way to address it, and then it simply passes into an age-related issue, not a death warrant.
In the past 10 years I have seen various things crop up - all of which sounded like a possible end-of-the-road scenario for many elans, but each of them have been addressed in one way or another by the resourseful owners, and passed on to the rest of us.
I fully accept that if you own a well-maintained and protected SE/NA elan, then you may still be driving around on original wishbones, top links, brakes, fuel tank, etc - and have no rust evident in your outriggers, chassis, seat mounts (which actually ARE outriggers!) and door hinges..... but many/most of us are not that fortunate and have had to address the known issues at some time during their life.
At one point it was the rear wishbones which were the major problem area, then once they were changed it became the front wishbones, then a possible problem with the fuel tank was discovered, etc etc etc.
The current area of concern is the rusty sills, but it is now becoming (or even has become) a documented repairable item - albeit that we'd rather not have to do it if it can be avoided.
I actually believe that the next 'elan killer' will be the lower door hinges - once they rust away that's it

(over the past 6 years most rusty hinges have been addressed by changing the whole door - but now there are none left

)........
.......except a couple of us have done (or had done by someone else) a fairly simple welding repair which requires a total strip-down and partial dismantling of the bonded sections of the affected door (along with associated repair/reassembly) - not quick, quite fiddly to get right, and makes absolutely no difference to either the drivability or cosmetic look of the vehicle (hence it may get ignored or put off until it totaly fails, which is a shame, because early repair is far easier that late replacement!) - but if it rusts to a point of becoming non-rigid, your doors will droop when open, and (more importantly, really!) the side-impact protection becomes virtually nil as the metal brace in the door isn't attached to anything.
So now I'm just waiting for the next issue to arise, as all of the currently-known problems have been assessed and repaired as necessary - but something else will undoubtably become an issue fairly soon. Then it'll be addressed, sorted out, and the elan will creep slowly towards it's telegram from the queen.
(This was meant to be a message of encouragement, but reading it back it sounds more like a quote from Pvt Godfrey "We're all doooomed".)