Quote from: Omega;9611353: You cant do that. The systems are too different.

I understood the OP question like that:

Quote from: Weru;830666Did the mixed level of character detail work out? Can one player play a B/X [style] Fighter, while another plays 3.5 [style] Half-Orc Rogue/Sorcerer/Paladin, while a third plays a 4e [style] Shardmind Battlemind at the same table?

Quote from: Dirk Remmecke;962115I understood the OP question like that:

Me as well. A B/X (never tried that system) Fighter is basically a Champion Fighter that uses all their Ability Score Increases to boost their stats. A half-orc Rogue/Sorcerer/Paladin [3.5 style] is certainly do-able with how easy Multiclassing is (assuming you have the requisite ability scores to do it) AND it's probably better than an actual 3.5 half-orc Rogue/Sorcerer/Paladin since you get more spell slots and the Paladin isn't bound by alignment AND the way Smiting works with all spell-slots AND being able to use Armor while casting spells AND not getting penalized with a -2 Cha that 3.5 Half-Orcs got... A 4e [style] Shardmind Battlemind isn't accessible (yet?) because Shardminds aren't an official 5e race. The Battlemind though could essentially be made with options from the Unearthed Arcana Mystic and either the Order of the Avatar (armor, psionic powers that boost combat) or Order of the Soul Knife as it would compliment the Battlemind-style fairly well. And I'm sure with the deluge of material on the DM's Guild someone, somewhere, already made a conversion of the Shardmind OR just use the ideas listed in the DMG to make your own race and get a copy from the 4e version.

The question though is can all these options be used at the same table, at the same time, and run coherently. Personally I think that's a resounding YES. The way feats and ASI (ability score increases) work, there's a lot of leeway in terms of overall power curve. Feats give you a bit more robust set of options but having straight up better stats puts you for better averages in terms of saves and contests. proficiencies are nice, in that they open some doors but there's lots of ways of doing that like Multiclassing or picking a race that already starts with certain proficiency (dwarves and armor or Elves and swords, etc.). Neither of the 3 options listed are going to have a significant advantage over the other on general terms. The B/X Fighter is going to be a solid steady DPR-mill with bursts of damage via Action Surge and a better Critical hit range and his saves will, eventually, be amazing by having Str, Dex, Con, etc. all near or at 20. The Rog/Sor/Pal will have greater usefulness in it's versatility with spells and skills but not hit as often and will occasionally run into option paralysis (because apparently that's a thing?) because they'll chew through their slots via Smite or other spells. Not to mention that they're stuck with a light weapon if they want to utilize the Rogue's Sneak Attack. The "Shardmind" Mystic will be pretty much Psi-Points heavy and give the player a decent amount of round-by-round options that will facilitate a better 4e-like feeling than the other two players are using.

I'm playing in a modded 5e game on weeknights; we use d6/side initiative and I think the DM is about to switch to classed XP tables, upping XP rewards for treasure/magic.  5e is very adaptable.  It is not my favorite D&D by far but it is my second favorite D&D (at the risk of being too reductive, I'm broadly grouping OD&D and AD&D under "old D&D" for the sake of this discussion).

IMO, the best way to replicate the old-school fighter is to play a Champion and take Resilient (Wisdom) at level 6.

Thanks to limiting spell interactions, bounded accuracy, and not front-loading classes, there aren't really ways to unlock gonzo power, therefore you're not comparatively punished for going simple. A paladin who uses all his spell slots for smites is going to be very effective. The Thief is quite hard to kill, delivers incredibly deadly hits, will pretty easily clear most traps and locks, and there's not much more to it than that.

The system is built out of a fairly simple set of core building blocks, so as long as you don't screw with that core system (e.g. reintroduce stacking modifiers), it's pretty robust.