Sorry but "I used to work in the business" doesn't in its self carry much weight as an argument. If you used to work in the business and are an expert on the topic you should be able to present a reasoned argument backed up with citations.
Here's an article on the topic of Bewl water allowing lure fishing.
Any Method At Bewl - UK Predator Angler
Seems to support my point than the "I'm an expert of the topic and so can with authority that I'm right" style arguments that seem so popular round here would.
Bibury trout farm let's kids fish for trout and pay around £10 per kilo. Are you suggesting that they'd make less profit if they scaled up their business?
Around 30 years ago, myself and 9 others had a decent sized pool dug out on the land of a farmer we knew, Before we had even thought of stocking it ( more of fish to stocked later) we had to put aside money for the first years rental, negotiate the cost of hiring his digger and driver, any removal /dispersment of waste soil and anything that may come to light in digging the pool, We started off by each putting £200 into the kitty, Then came the cost of plants, water testing samples, all this before we had even put a fish in it,
The fish that were going in were from a reputable fish farm, all health certified, We even had a clubs fisheries manager on board for advice.
The fish that were going in initially were tench, some crucians silvers and perch, No carp because we did not want them hybridizing with the crucians, that £2000 did not last long before we put more money into it.
This was not done as a money making venture, it was done so 10 blokes and if any spaces on the day their immediate family could fish.
If we had done it as a day ticket water, we would be on a loss for quite a long time, there were insurances to consider, VAT, strict safety aspects.Also once stocked it was not fished for 6 months ,this was to acclimatise the fish and also to see if any fatalities showed up.
So if you think with your "I'm the expert view" digging a hole in the ground and bunging a few fish in yhen waiting for the money to come rolling in , You go for it.
Or take the word of someone who has done his homework and found it is not viable .