Regarding maps, I can say that it was what originally put me off from buying the game, along with the complaints about a limited inventory and crappy UI.
After playing the game, those things didn't bother me nearly as much as I thought they would. Scarcity of maps was a non issue, limited inventory is a non issue and you get used to the ghastly consolized UI.
I suppose I would agree that what is the point of including the map mechanic in a trivial form. They should have limited magic maps by making them more expensive or something. On the other hand, the mazes usually have no logical structure so navigating them without a map and trying to memorize it all would be a pain in the ass. For the record, I played with no mods and kept 1 inventory slot with 9 maps, as well I had 1 mage caster that eventually was able to cast the map spell 9 times. That was enough for me.
I played with ~10 open inventory slots, no bishop, no mysterious bag and the treasure chest ex-skill. There were a few times I had to reject loot. What I usually did was go through my inventory and chuck all the medicine and junk with a quantity, then pick up new loot. I usually abandoned 1-3 items in a run. No big deal really. Then I acquired teleport and it wasn't an issue at all.
Concerning the Bishop and his role identifying items in the game, my habit was just to use the pre-made Bishop in town to identify all my items. When he got low level I demon-grinded him up until his identify started to work again. I've never brought the Bishop along in my party. Also, you can shop-identify all items, they cost exactly as much to identify as you get for selling them, so all it means is you didn't make a profit from items if you use the shop. The only use I can see for the Bishop actually being in the party would be his ability to identify items as you are adventuring, which would allow you to discard lower quality items and take more better ones back to camp, as well as being able to use better gear you find while on the same dungeon run. While helpful, neither of these benefits are a "must-have" for me. Also, the Bishop has to be an insanely high level to identify items well or he will fail alot, which is super annoying. I usually just have him identify the bulk of my loot and then just shop identify the harder items to save time. Absolutely no issues with money.
I used an Alchemist until he was level 28, then I benched him and used him in exactly the same way as the Bishop. Unlike the Bishop, alchemy spells are essential to the party - but you don't have to use a pure Alchemist to get them.
Actually, before I discovered the ability to demon-grind, I always thought the purpose of including these 'must have' skills was to encourage you to make multiple parties. Your main party full of bruisers and badasses, and a support party that you leveled up to give you access to identify, disassemble, mixing, etc.
Lastly, let me just say that aweigh is a dirty rotten liar the Thief is not required to deal with traps in Ibags tower. The only time I ever noticed failing my traps was at the beginning-mid part of the game, not the end. Ninja is 99.9% effective on final floor of the tower. He must answer for this.