The front panel is pretty restrictive, so adding fans would help, but probably not to any great degree.
Normally, with a restrictive front panel, you'd want to be exhausting as much hot air as possible (negative pressure), but in the MBLite3.1, they've closed off the top panel too.... so you're very limited.
The PSU should usually be it's own eco-system. Fan facing down, drawing cool air in for itself, and exhausting out the back. In restricted environments (or when directly on carpet), it could be used as another exhaust, drawing air from inside the case, and exhausting it out the back.
Honestly, if you're thinking of upgrading to more powerful components, I'd consider replacing the case too. You could always test as-is, and add a couple of intakes at the front, but I'd be stunned if it made a significant difference.
Considering there are fairly cheap cases with better airflow, that would be a good route to go, IMO.
Something like the MX330 is <$40, and has decent airflow.
https://pcpartpicker.com/product/vYp323/cougar-mx330-atx-mid-tower-case-mx330