Useful features for endgame analysis

[jwes]

I have been working through Basic Chess Endings with my computer and there are some features that do or would make analysis easier.
1. Verified null move. I know in general it may not be worthwhile, but it appears that many if not most difficult endings involve zugzwang.
2. EGTBs. Again they may not help in general, but I am convinced they do in endgames.
3. MultiPV. Not necessary, but very convenient.
4. Better hash handling.
a. full PVs like bob has been discussing.
b. hash cutoffs in PV nodes.
c. some form of persistent hash. The simplest idea I could come up with is storing the root position in the hash table with a flag which says "don't overwrite this with a different position".
I see b and c in the following situation: I analyze down a line until I know if it is win, lose, or draw, then I back up looking for alternatives. Without PV cutoffs, the program spends time researching and the score jumps around (try this with stockfish to see what I mean). If I go down a variation, it is not unlikely that the hash entry for the first line has been overwritten, which is why I would like persistent hash.