What's achievable with no talent but some solid hard work?

I'm a 40f. I'm a serial beginner whose training is more 'off' than 'on'. I've never broken 60 mins for 10k. My 5k pb is 29 mins and my half pb is 2: 15. I was the kid that was last in gym. My right ankle severely overpronates so I wear support shoes that help a bit. It still rolls slightly with that but doesn't hurt at all. While I run 'funny', I do now recognise that my lack of consistency is as much (more?) the cause of my rubbish results. What I'd like to ask is what times could I reasonably aim to hit if I did consistently train 5 days a week for (eventually) maybe 40 -50 miles a week, with the support of a running club and decent coaching?

I have a marathon booked in 30 weeks so I'm starting my training (Hal Higdon) in earnest tomorrow where my goal will be just to get around and enjoy it. However, instead of 'resting' afterwards, I'm going to join a club in a few months and keep going with a view to seeing what a couple of years of consistency could achieve. Sort of a personal experiment to see what effect hard work can have when you have no innate ability.

So, please, what could I (should I) realistically expect to run say in 2.5 years of consistent training? I'll be 43 by then. I'd love to have this in mind going forward and see if I manage to hit those standards in the end. Sort of a benchmark to try and hit that isn't outrageous but requires me to keep working towards consistently.