Ok here's my view.
You have paid a lot of money for the BMW experience.
What you have had has been a string of failures, culminating in your second bike engine terminating itself.
BMW will not give you a refund - you have had some use of the motorcycle, so it would be a very difficult thing to get.
But what you paid for was a brand new motorcycle, not a freshly rebuilt motorcycle on its second engine. Such a motorcycle would get less money second hand - the new engine will breed suspicion for any prospective private buyer. Only a dealer could get top money for this bike.
So either BMW should consider some compensation for this, to issue you with a new bike. Remember, you paid for a new bike, not a newly rebuilt 6 month old bike.
When my bike failed, it quickly became obvious that the dealer had done as much as they could, and BMW customer service denied that it was anything to do with them.
Rather than prolong any to and fro discussion, I wrote direct to the MD of BMW group UK - I went straight to the top.
I was polite, but stated calmly and clearly exactly what happened ( my camchain broke), In your case, explain what happened and when. And while the problems are to be expected, you are not happy that you will end up with an bike that is no longer new, but rebuilt.
In any letter to the HQ, keep your cool, be very calm, and don't rant. It might make you feel good, but won't help your case. Be clear what you want ( and make sure it is attainable and reasonable), for example, a new 2014 bike would be reasonable. A refund, probably not, because you have done some mileage...
Don't even start on the "if I pay £1000 more to upgrade..." lark, doing so will only show that you aren't really serious. A serious position is that you bought a new bike, not a rebuilt one - so it is reasonable to ask for a replacement - not a second hand one, but a new BMW - this was, after all, what I paid for.
If this replacement happens to be a 2015 machine, so be it, but if they find you a 2014 model, that's not a bad result, and is one worth taking.
Swapping to another model is a possibility - you have to ask yourself what you really want, and what would be the best option for you.
Personally, I think the LC is a cracking bike, so I'll give it another chance, but it sounds like you are fed up, so I would understand if you wanted out.
Perhaps you should think about the cheapest way out - this could be pushing for a new bike, and sell it straight away ( yes, at a bit of a loss, but it could be the best of a bad bunch of options) but don't let on to BMW that this is your plan, or they will not play ball. Best play would be to say that the GS is your life's dream to own, and you really want to have your confidence in the bike restored, but at the moment, this confidence is in tatters, and you ask BMW to resore this.
P M me if you want any more info...