I have some ideas for a few relatively far-reaching changes. The big question is whether they are radical enough that they warrant a fork (of V or v4) or whether inclusion in v4 is reasonable. To begin with I want to motivate the problems I'm trying to solve.
1) The length of the second half of the dungeon is too long, and gameplay tends to be monotonous. This is only countered by the enjoyment of being in the deep dungeon assuming you are unfamiliar with it. (This is the standard operating assumption of Angband, it is not true for me.)
2) Unique monsters are too strong. They can rarely be handled at depth.
2a) There is not enough incentive from dealing with uniques, particularly late game uniques.
2b) On the other hand there is incentive to wait to kill uniques until deeper in the dungeon for better drops. This is the standard gameplay strategy.
3) Monsters come in groups that are too large (and tedious to deal with). Group monsters are also too ubiquitous in the dungeon.
3a) Later game escorts are absurd. 20 pit fiends or greater balrogs are not an interesting challenge. They are an impossible challenge.
3b) Z monsters are too powerful. Always awake + breathe for way too much damage make these groups uninteresting and not fun.
4) Monster summoning is too powerful. If two Great Wyrms of Balance are too much for one player to fight at once, one should not be able to create another.
5) Teleport other, destruction and banishment are too strong. 4 and 5 are interrelated. You can't weaken the players counters to summons without weakening summons.
So here's what I would like to do -mapped to the above issues.
1) Reduce the dungeon to 50 levels. This may involve removing some unique monsters, but that's not entirely necessary.
1a) The mapping would proceed something like this.
Current Angband Smaller version
1b) This step is probably the final step I would take, and the most likely to require a personal variant, especially if it involves removing monsters.
1c) Sauron lives at 50, killing Sauron causes Morgoth to spawn on the level.
2) Lower the strength of uniques. This would mainly be accomplished by reducing hit points. An increase in the incentive to kill uniques is discussed in 4).
2a) Make uniques guaranteed to appear on their rated level. A player that wants to systematically kill all uniques will be able to.
3) The main goal is to provide more customization for how large groups are. This is likely to be the least controversial, so it's probably what I'll start with. (It's also the hardest for me to implement)
3a) Allow specification of what monsters appear with given monsters. The clearest example would be to have the three trolls Tom, Bert and Bill appear with each other. But also Gothmog appears with Lungorthin and a couple other Balrogs. (If Lungorthin is dead, Gothmog is that much easier to handle)
3b) Allow different magnitudes of how many friends should appear. Novices can come in smaller packs, but orcs can still come in larger ones. Size should be dependent both on danger and how annoying it is to deal with a large pack. 'Z's are annoying, 'o's are not. The argument is that large packs of 'Z's are bad for game enjoyment but large packs of 'o's are ok.
3c) No spawned group monsters.
4) Major changes to summons and player abilities are called for. First for summons.
4a) Monsters that tend to 'summon' other monsters instead appear with one as an escort. Enchantresses are accompanied by a dragon, Mystics come with spiders. Rangers get some dogs.
4b) Most summons get replaced with 'calls.' A call brings a monster somewhere else on the level to the summoner to assist in the battle. A called monster must not have LoS to the summoner (or maybe the player because that's easier).
- I've considered having a called monster gain HP back at the expense of the caller if it was injured, but I'm not sure whether this is a good idea or a pointless one.
- Calls should be a preferred attack if no other monsters are in LoS of a call-capable monster. The goal would be to first kill the escort, then the summoner.
- Failed calls should not be repeated.
4c) If no monsters are available to be called (all dragons on the level are dead) nothing is summoned. The call goes unheeded.
4d) Monsters can still summon (read: create) a monster but at some penalty to themselves. I was thinking a HP penalty related to the level of the summoned monster. Monsters will not use this summon attack if their HP are below some threshold. Very few monsters have this ability (Qs and some Uniques).
4e) Summon Uniques is unchanged. Only Sauron and Morgoth have this spell. The uniques come at no penalty. Other non-unique summons arrive with the same penalty for Sauron and Morgoth. If all uniques are dead, Summon_Uniques brings nothing.
5) The major nerfs of summons are accompanied by major reductions to the ways for the player to dismiss monsters it doesn't want to fight.
5a) Monsters get a save against teleport other. The save maxes at 50% for Morgoth.
5b) Destruction does not remove monsters from the level. Monster can save and be teleported elsewhere on the level, or just outside the destruction zone. Destruction zones are smaller (radius 10 instead of 15). Destruction will not work on level 50 until Sauron and Morgoth are dead.
- Destruction spell is only available to mages and priests.
5c) Banishment disappears entirely. Mass banishment works as a mass-teleport other of everything within N squares without a saving through. N must be larger than max-sight (uniques excluded)
Some more miscellaneous changes.
Monsters can forget about the player and fall asleep. (I'd like to implement wandering monsters, but that might be beyond my ability.) Spawned monsters can appear asleep, or maybe eliminate spawned monsters altogether?
Increase the divisor of many breaths. Time, Gravity and Plasma top this list, but I would also consider Nether, Shards, Chaos and Inertia. A pack of 6 time hounds that only breathe for 30 damage are still something you avoid.
I have a far goal of implementing permanent levels, but I know I don't have the skills for this right now.
Allow probabilistic drops. Sauron gets a 2% chance of dropping the One Ring. Gothmog has a 50% chance of dropping his whip, etc. This also includes normal drops like spellcasters dropping books, molds dropping mushrooms and so on.