Adhering to older, preferred styles is exactly why the scene is the way it is. And 1850 is a lot of work, true, but it is the tournament scene (and how it brazenly speaks for the entire length and breadth of 40k all the time) that have made this a standard.
To new players who've never played a previous edition, the detachments mechanism will be a non-issue. As a store you want NEW players, not established ones -- established ones use the same models for 10 years, and grumble whenever things change such that they have to adjust. These people do not buy models like new players who want to try everything, or new players who are building armies without the constraints of old fluff or prejudices. It's a win-win all around -- the business flourishes, the meta shifts, everyone works on their armies and thus buys more, and things just generally flesh out and stop being stagnant.
Not to mention, whenever you add arbitrary restrictions, you are just bolting rules to rules. For example, the CAD+Allies thing a lot of tourneys are doing now, basically states [The Normal rules], but for this event [the event rules].
I mean, look at the Battleground event announcement. It is littered with various bits in there for full disclosure. To me, if an event has that much stuff that you need to clarify, it is certain to be off-putting for new people.
Were it me, I would pair a lot of these things into general Battleground policies, and reduced to simple links in the announcement. I would also try to generally do a little less, if your goal is to be inviting. Here, have a look:
This event will be capped at 18 players.
Rule Books:
The Warhammer 40,000 SEVENTH Edition Rules will be used.
The following is a list of legal army choices:
Codex: Blood Angels
Codex: Chaos Daemons
Codex: Chaos Space Marines
Codex: Grey Knights
Codex: Dark Angels
Codex: Dark Eldar
Codex: Eldar
Codex: Imperial Guard
Codex: Imperial Knights
Codex: Necrons
Codex: Orks
Codex: Space Marines
Codex: Space Wolves
Codex: Tau Empire
Codex: Tyranids
Codex: Adepta Sororitas
Coedx: Inquisition
All **faction specific** supplements and dataslates will be allowed in this event unless otherwise noted. You will have to provide those rules to the TO upon submission of your army list, however.
MODELS AND POINTS:
1. Each player must bring a BATTLE-FORGED army consisting of 750 points or fewer (735 min), in accordance with these rules.
• Armies may be constructed from a maximum of 2 Detachments (as defined in the 40K BRB), no more than one of which may be a CAD.
• Allied Detachments may be selected from the same Faction as the Primary Detachment.
• Formations are permitted as one of the 2 detachments, but not Apocalypse or Fortification Formations.
• Detachments may be produced from a maximum of one Codex / Codex Supplement.
• A limit of one Imperial Knight model is allowed.
Selected units that alter Force Organization selections WILL affect all other detachments from the same codex. For example, a Space Marines Master of the Forge allows all detachments using Codex Space Marines to take Dreadnoughts, Venerable Dreadnoughts and Ironclad Dreadnoughts as Heavy Support choices as well as Elites choices.
2. All models must follow “What You See Is What You Get” (WYSIWYG). All weapons, war gear, and so forth must be represented on the model unless otherwise approved (see number 3). Your models do not need to be painted but they do need to be FULLY assembled.
3. Pictures of conversions or "counts as" models must be emailed to the Tournament Organizer. There is an expectation that your conversions or "counts as" models are "hobby quality." No "toys" will be allowed.
4. Psychic Powers - There will be no changes to the Psychic Phase or Psychic Powers for this event.
5. Forge World and Imperial Armor lists that are 40k Approved will be legal for this event. If you list contains FW or IA models, lists, or units, you MUST submit the rules and point cost for them when you send in your list.
At the event, players MUST have a hard copy of the Forge World / Imperial Armour rules if they wish to field that unit. NO EXCEPTIONS.
6. Lords of War will not be legal for this event.
7. Fortifications - Players fielding fortifications must provide a hard copy of the rules governing the chosen piece (from Stronghold Assault) and be familiar with the FAQ where necessary. The following Fortifications from Stronghold Assault will be legal for this event:
• Aegis Defense Line
• Imperial Bastion
• Skyshield Landing Platform
• Firestorm Redoubt
• Vengeance Weapons Battery
8. We will require that each player submits his army list to a Battleground Tournament Organizer on or before Monday, September 22nd (roughly a week before the event). We ask that players email their lists to ChaseLaq@gmail.com as soon as they are finalized. We are going to do our best to check every list before the event begins.
9. If illegal units or other rules violations are found in a player’s army list, at a minimum, the models in violation will be removed from all subsequent play. In addition, tournament points may be deducted and/or award eligibility may be forfeited. If in doubt, please ask for clarification in advance from a Battleground Tournament Organizer.
That is a wall of text that even I as a seasoned player look at and go, "Meh." At heart a tournament is supposed to be a few rounds of 40k with scores for winning, playing nice, and looking nice. This whole thing is overly concerned with specifics and it makes me not really want to bother, because it is clear the community has a VERY specific way to play. I know it is barely different from most places, of course, but that is not what people think when they see 10 paragraphs of additional rules governing the army you can use. They think, "Wow that is a lot of stuff. Meh." and don't bother. This is how you end up in the predicament that only people who really want to play in tournaments come to the events; they will play regardless of restrictions or rules (and will complain about them afterward regardless as well). There's no point further catering to that crowd and continuing to isolate the meta game to the top 5-10% of players.