the Jester
Legend
My answer remains pretty much "play by the rules".Here's a simpler question along a similar theme: having already spent their action and bonus action, a player needs their character to move 35ft to get out of danger, but they only have 30ft of movement. Is there a test you would consider that would let them make the distance? For me the answer is yes: DC 13 Athletics check, failure condition is probably Prone, unless something else in the scenario seems like a better fit.
A character wants to move more than their speed? Dash. That's not enough? Well, let's hope they make it to next round.
You can move your speed. Not your speed + 5'. I wouldn't allow a monster to do this (absent some special trait or something) either.