Well, something needs to be done about XP and levels.
Either the pace of leveling can be slowed dramatically - you can do this yourself with the in-game config menu in Project Nevada - or the level cap will need to be increased. For me, slowing the leveling would make the game more boring.
To go above level 50, there are four tasks that need to be done:
Skill benefits above skill level 100
otherwise, what does increasing your skills really do for you.
Increase the hard level cap
otherwise, you hit max XP and getting more XP doesn't count toward your next level
Fix the level up screen
otherwise, it doesn't work right when you go above the level cap
Debug the game
so that any conditionals that might use the function "GetLevel" still work for characters with a level over 50. According to some of the posts I've read, the level 50 max cap is "hard coded" (whatever that means) into various places in the game, so it can be difficult to deal with. For example, three dog will stop talking about you on the radio after level 20 (fix for that issue for FO3).
For Fallout 3 there were several mods, all of which needed to be used together:
Wasteland Mastery - gives skill benefits above 100, up to skill level 250
Level Cap Workaround - allows you to level up past the level cap of 30
Level Up No Lock for FO3 - makes the level up screen work past the level cap of 30 - or alternatively, Level Cap Increaser
For Fallout New Vegas, there was a similar set of three mods that basically do the same thing:
Boosted Skill Effects - gives skill benefits above 100, up to skill level 255
Max Level Adjustment - allows you to level up past the level cap of 50, uses NVSE as described here.
Level Up No Lock for FNV - makes the level up screen work past the level cap of 30
Alternatively, you can use Project Nevada's rebalance component to manage all of your leveling settings, and then use this PN uncapper mod to raise PN's max level from 50 to something higher.
I haven't tested any of these various uncapper mods myself so obviously I don't know if any of these even work properly.
It would be great if we could come up with our own "TTW level up mod" that took care of all three of those things and was fully compatible with TTW.