I’ve played D&D since 1e though skipped 4e and played 3e/pathfinder during that era and have played 5e close to RAW since it came out. Two of the rules which are supposedly in place to keep a lid on characters getting too powerful are the magic item attunement limit and concentration mechanic. I plan to get rid of attunement and rework most of the phb concentration spells to enable upcasting the spell to cast it without concentration and here is my thinking on both.
Bear in mind this is obviously a discussion about homebrew rules so I am not considering adventurers league, nor am I calling the current rules dumb they have to work for a wide range of tables including open play games I’m talking about changing them in my games which are long term games/campaigns that run with for years and across all levels.
Attunement is meant to act to control the amount of magic items a character can have but whether they are attunable or not is largely irrelevant to the impact the magic items will have in the game. +3 plate doesn’t require attunement, boots of levitation do (and using them requires concentration btw). In practice the attunement limit is only relevant if the GM gives out sufficient magic items that it comes into effect (if they don’t it is irrelevant) at which point it’s effect is to stop the players from getting to use some of the magic items they have found unless they aren’t using others they have found. I largely believe the obligation to balance items given out is on the GM- this is how it worked from1e-3e and still should be the case. Also getting to use the treasure and the magic items you find in the game is one of the fun parts of the game. Thus imo the attunement limit in a practical sense works more as a limit on fun than other stuff. My high level character with his belt of dwarvenkind, pearl of power and staff of healing isn’t that interested in the cool wand of web - it’s not overpowered for sure but I’m not going to waste an Attunement slot on it, maybe I can trade it for a third wand of magic missiles they don’t require attunement?
As for concentration; in the game of Bushido They limited spell stacking by saying that certain spells couldn’t be active on the same person at the same time ie no stoneskin and resist elements. This wasn’t a bad way to limit spell stacking. In 5e they’ve gone the other way by saying that your limit is based in the number of casters you have. Like attunement I see this as not a big deal at low level but at higher level begins to suck the fun out of the game. The fighter needs stoneskin because we are fighting giants so the Mage can’t fly or be invisible or cast a wall spell ok I guess I’ll just cantrip or lightning bolt each round. Having played earlier editions I’m aware of the problem where the caster starts each combat with 7+ spells up. This meant that the difference between the characters who had a minute to prepare and when they didn’t was vast making balancing encounters very difficult. Ie In 1e - 3e If the party is ready to fight the 4 chimera and their fire giant beastmaster it’s a tough fight, if not they will get smashed. This is less so in 5e because you can’t overprepare. However in 5e characters have very few high level spell slots, and not an over abundance of low level ones they already have a massive limitation built in. So what I have done is go through the phb and for most concentration spells I’ve allowed a caster to rid themselves of the concentration requirement by upcasting the spell 1-2 levels. So web cast as a 3rd level spell doesn’t need concentration, same with blur cast as a 4th level spell, greater invisibility when cast as a 6th level spell. I’ve kept concentration as unremoveable for some spells (spirit guardians for example it lasts a long time otherwise ).
With both of these I acknowledge they empower players a bit more but I’m not worried about game balance issues - it’s a home campaign and I can handle that side of it.
I hunted around a bit to see how others have dealt with these issues but couldn’t find much so I’m posting this to see what others have done and what they think.
As a long-time 1E/2E player, I completely agree. I greatly dislike the concentration mechanic and think attunement is a complete waste. Whatever a table does to remove or de-limit these aspects of the game is an improvement IMO.
For my take, remove attunement entirely. As DM you certainly control how much magic is in your world. Our table is thinking about going to a super-gritty very low magic game next. We prefer it that way. Personally I don't like "mundane" magic items. I prefer fewer items, but when a character gets something, they are likely to keep in an not "upgrade" as upgrades simply don't happen that often.
For concentration, given how few spell slots casters get compared to 1E, especially at higher levels, I would remove it entirely. Your idea of casting it using a higher level slot is perfectly fine to me as well. IME concentration spells are rarely broken anyway. The biggest thing it does is limit casters to having one at a time. If casters want to blow all their spell slots by casting lots of buffs, go ahead, you'll regret it later.
While others might not like the idea that a spell, once cast, is in effect unless dispelled (damaging the caster really shouldn't stop the magic from running its course IMO), and that is one of the things that made magic so powerful and feared.
CoDzilla is a problem created in later editions. 1E/2E IS FINE and no game I've ever played in using those editions had a problem with the power-difference between casters and non-casters. Even the quadratic-wizard/liner-fighter idea is overblown IME and IMO.
There are other ways that 5E is subject to abuse, but it has reigned in a lot from 3E, etc.
Anyway, if you want to keep concentration in some form there are lots of ways to do it. Higher level slots, a greater limit on how many concentration spells you can have at one time (limited by tier, spellcasting modifier, a new feat, etc.), maybe checks only on critical hits (normal hits are nearly always a DC 10 save anyway...), have concentration saves made with disadvantage for each spell if you have more than one, allow one "free" no check required spell, and the second makes saves required when damaged, etc.
In our session yesterday, a player who will probably be our DM next in rotation, was asking why not have a feat that allows multiple concentration spells, at least two? Well, the problem with that is many caster characters would end up taking it--and no feat should be that vital to so many characters.
Ultimately it comes down to this: whatever you do for the PCs works against them as well. If the players are ok with an enemy wizard not having to concentrate on spells, or not having a completed spell disrupted when hit, etc. then everything is fine.
Personally, as much as I enjoy 5E, there is a whole bunch of 1E that I miss and think a hybrid between the two would be best.