Need advice on basement flooring

5 months ago I bought my first home - in Calgary Alberta. We were excited that it had liveable space in the 'fully developed' basement - a place where we could have an office, a spare bedroom and a family room. It wasn't the best - but it had lots of potential. There was no musty smell (like many of the basements we looked at) and seemed relatively warm - even in the subzero Calgary weather. The only thing is that the wooden floors had some spring to them, with slight uneven-ness in areas, and the carpet had seen better days.

Recently we got a shocker. What we thought was a 'fully developed' basement - as per the listing - is actually what I would call a partially developed basement. We were prepping to pull out the carpet to lay vinyl plank and take off the warped subfloor and level it - only to discover that below the wood subfloor is just earth - like a cellar. We had been under the assumption that it was a wood subfloor on a concrete slab. This wasn't caught on our inspection, nor did the seller divulge it.

Now we need to figure out a solution. And I'm entertaining a multitude of options from more expensive and long-term, to a quicker fix.

A little bit about what we found. When we unscrewed and pulled up a section of the subfloor beneath the carpet - an access panel - we could see that the floor consisted of 2x4 joists that were raised slightly off the dirt floor with other pieces of 2x4, creating a pocket of about 4" between floor and dirt. No vapour barrier could be seen. But from some investigation - it seems like there are concrete footings around the perimeter upon which the interior walls of the basement sit. Shockingly - they don't seem to be rotting at all.

So of course we can pour a slab down there - that's a more permanent fix - but could be costly. Although this is only a 1200 sq ft home.

The other option is redo-ing the wood floor over dirt- but higher quality and level. From what I've read, if you do that, you should lay vapour barrier, gravel/sand, and put the joists on concrete footings or paver stones, like a patio. I'm guessing they tried to keep any footings minimal as to preserve the height in the basement. I'm wondering if there was a reason they didn't put vapour barrier down - ie: issues with ground water table. But without moisture indication - rotting beams, moisture in the carpet etc - I'm not sure things are wet down there. Like I said at the start - we were so happy this place didn't have a musty basement smell like so many others.

The last option of course, is try and save what's there - keep the joists, but pull out any warped subfloor (its also cheapo OSB board) and try and level it as best as possible so that new flooring can be put down, vinyl plank or stick on vinyl/lino. Carpet isn't an option as my wife has bad allergies and doesn't like it. And buy ourselves a few years before we undergo something more serious like a slab pour.

Thanks for taking the time to read. Any advice / suggestions would be appreciated!