Devils advocate here... like it or not you never see a poor farmer, and it's a closed shop.
Perhaps this might allow some new entrants?
I know poor farmers, I know rich farmers and I know farmers that appear to be doing unbelievably well who work 18/7/365 doing the farm and outside jobs to pay mortgages for the expansion of farms.
The IHT for farms is a joke...... Namely because it's abused by multi millionaires who seek a tax dodge for the next generation. That hasn't changed. Richy Mc Rich will still buy a farm and be a "farmer" because it's a desirable life choice and still comes with tax benefits.
The only way to nail it fairly is do do it on land size.... To me 150 acres is workable as a farm if your actually in it to farm. Lots will disagree, but my grandfather grew up on around 50 acres and it supported a family of 5.
150 acres per person..... So if Dad has a 300 acre farm and two kids they don't pay IHT..... It's fair, effective and protects farming, each 150 acres gets the properties connected to it, farm hedge and have 2 workers cottages that the workers live in? They are farm buildings..... No IHT.... But as a minimum, farmhouse, farm buildings and 150 acres. If you can't succeed with that start then No, you don't deserve to be farming.