Battery chargers in parallel

I have two of these https://lunacycle.com/220v-luna-charger-52v-advanced-300w-ebike-charger/ guys working for me last few years. Seem stable. Early on I cut holes in the top plates and put in much larger adjustable fans to reduce the noise and improve cooling.

Would it be possible to (reasonably safely) hook the output of these in parallel, both set to say 5A, for 14s charging @10A? What could possibly go wrong?

I don't see why you can't do that. As long as both chargers are set to the same voltage, it should be fine. During the CC phase, both will be running at their CC limit and share evenly. As the pack gets full, one will likely be slightly higher than the other one and do all the work, but this isn't a really problem.

My only concern would be if the cells can handle this charge rate.

Thought so, always nice to get someone else's input too. These chargers actually reliably produce ~430w or almost 8A on their own, with just improved cooling and a little potentiometer dialling.. I don't know their upper limit as I haven't pushed it further.

Target is a 14s2p pack of 10Ah Turningy bricks on a BMS, would handle pretty large charge currents when charged in a safe place.

I would have assumed these chargers would not be DC isolated? If they are DC isolated, then they will probably work. If they are not DC isolated, then they will short out?

Isolation is only needed when putting them in series.

(or if paralleling supplies plugged into different sides of a house breaker box).