I mean, I don't really think we are voting for anything here, since regardless of what we want they going to make their own decision :P
I would probably do something like this. Party XP is divided by 1+the total number of characters in the party. If there are 4 party members, its divided by 5, if there are 5 party members, its divided by 6. You get the idea. This creates a slightly more compact XP spread than if you were straight up dividing by the number of party members. A party of 1 would only earn 3.5 times as much XP as a party of 6. They would obviously balance the XP awarded around the party size they want (in this case, lets say 4), but in my opinion, figuring out how to divide it is the more important part.
Lol fair. But in an ideal world, Larian would tally the "votes" expressed in the forums/steam reviews/etc to determine how loved/hated any mechanic is.
Sure, figuring out how to divide exp is the most important. If you do it correctly, you don't need to make any other adjustments to preserve balance.
However, I think that your solution is worse than an unadjusted exp division where you simply divide by # of party members. Keep in mind that 5e levels are not linear. Each level requires more and more experience. I think that this already works to create the "more compact exp spread" that you want, and your solution would double this effect.
e.g., A party of 4 that just reached level 5 (6500 exp). In a party of 2, each member would have 13000 exp, which is still level 5! A solo player would have 26000 exp, which is only level 7. I'm skeptical that a single level 7 party member could take on a CR 5 encounter....
In your solution, each member in that party of 2 would have [6500*(4+1)/(2+1)] = 10800 exp, which is even further from level 6. --a solo player would have 16250 exp, which is level 6. This person would get murdered by a CR 5 encounter. Seems like ^ would unduly punish small parties.