Based on my decades in the chip industry with $300K to $400K (at prices back then) high speed testers for all kinds of our company's high performce analog integrated circuits - including the "LMXXX" series of voltage regulators, my definition of "Warp Speed Charging" of RV batteries would be:
Use a power supply ("charger") for your RV battery bank that can maintain as long as necessary at the power supply's terminals the voltage for each charging stage that the battery manufacturer recommends for your particular battery bank REGARDLESS OF WHAT CURRENT THE BATTERY BANK WANTS TO DRAW at each charging stage.
This kind of charging sounds simple ... which it may be engineering-wise ... but it won't be cheap. This requires a power supply ("charger") with no voltage sag on it's terminals at any current draw up to and including the maximum safe current acceptance rate for any size and type of battery bank being charged.
For instance: The PD line of RV battery chargers comes with high recommedations from the RV community. However during it's 14.XX volt boost stage initial charging of say, a 440AH RV battery bank ... can you in fact actually measure on it's terminals 14.XX volts? I'm betting that the answer is "no". I'm betting that it's terminal voltage will have sagged down to some value (maybe well) below 14.XX volts during heavy current draw in it's boost stage when the batteries are at their lowest State Of Charge.
Notice my comments above say "on it's terminals" with respect to a charger's output voltage. But as a side note, of course one should use as large as possible cabling between the charger's terminals and the battery bank's terminals so that the battery bank's terminals see almost the same voltage as you measure on the ideal charger's terminals.
RV-world chargers that can do this probably are hard to find, may be large physically, and probably would be expensive. The ultra-expensive test systems from my work days had exactly this - power supplies that would produce at their output point exactly the voltage the computer program called for, regardless of how much current they had to deliver to do this.
Here's my real world mini-version of this situation which I'm betting is a common one: I use a good old not-recommended, fixed stage, Parallax 7345 converter to charge my RV's 230 AH battery bank. It's supposed to be able to deliver up to 45 amps. Well .... I never see my 50% depleted battery bank getting 45 amps from this charger. You know why? Because it's output voltage on it's terminals is nowhere near 13.8 volts when it's hooked up to my depleted battery bank. Now ... if this converter could actually maintain 13.8 volts on it's output terminals when charging my 230 AH low internal resistance battery bank .... boy, would my ammeter's readings change.
All of you who think you have a "14.XX" volt charger during your battery boost stage charging may want to confirm that this is the case by checking right on the charger's output terminals when it's dumping really large current into your RV's battery(ies).
I could be wrong on how good some of your chargers are, however.
2005 E450 Itasca 24V Class C