I think in your situation I would speak to a (very good) financial advisor because there may be funds where you could put your money away for some time that may give you growth. We have invested like this, and were pleasantly surprised how thorough the advisors were. And yes, we had growth in the capital, well over and above what is available on the high street (currently virtually zilch). However, this was a few years ago.
I sometimes wish I knew more about art and antiques because I think that is where there is money to be made, but, I digress. To me, the problem with mortgaged btl property is that the goverment has taxed it to the hilt, and, if you are managing it yourself, it can be a lot of hassle. Otherwise you will have to pay to have it managed, which eats into profit. Then there are the dreaded voids or troublesome tenants to contend with.
I don't know the answer I'm afraid. The only thing I can say is that life is short and it is better to enjoy yourself now, rather than waiting for some random time in the future when everything comes together (one hopes). Buying a property as a pension is very much 'eggs in one basket' to me.