Individual tables should be encouraged to change rules that aren't working for them. 'Concentration' is no exception.
Tweaking Concentration is not going to make 'casters too powerful' any more than expanding Banishment to effect any creature, or overpowering Fireball and Lightning Bolt intentionally, or adding in Counterspell and starting the whole Reaction/obfuscation mini-game. There are many options for dealing with enemy spells beyond the lowest common denominator of 'hit them for damage'. Incapacitated (stuns, sleep, hold, petrification, unconscious, dead), lesser restoration, save each round, dispel magic, counterspell, and saving throws in general.
The reality is that Wizards is not going to majorly revise 5e through errata. Talking about changes individuals want to make to personalize 5e for their particular table/group are not a threat to the 5e Rule Set at large or a push to speed us on to 6e.
5e is built to handle house ruling. It is by far my favorite starting point for the rules at my table. And 4e is my second favorite. If DMs want to try out house rules then it is to 6e's far-off future benefit that they do so and get some long term experience of how it plays out.
That's not to say it wouldn't have been beneficial to have another pass or two on the rules in Open playtesting before the Devs and A/B testers gave us the Ranger Beastmaster or took the elegance of the Bonus action and then multiplied it out to the point where players view it exactly like they were trying to avoid (constantly hunting for ways to use your 'Bonus action' like it is a standard part of the Action economy).
