Customer/Franchise cars have beaten the works cars in the past, even as far back as 2008 when they were in use last. Red Bull were outscored by Toro Rosso by 10 points, however the Ferrari 056 and a Sebastian Vettel were primarily the advantage that season.
If Customer Cars are on their way, id put them in a separate 'Teams Championship' and exclude them from the constructors title, they are almost excluded from the FOM prize money, only getting a share of €75m a season from them. They are also cost capped as well to a budget of €100m a season. The teams that go this way, however are given more freedoms in terms of track testing in season, they will be allowed to test for 6 days more than the established 'Constructors', however they must allocate 2 days of that over to the tyre supplier and their allocated test driver/drivers. This will help both the teams/tyre supplier. The other 4 days must be allocated to young drivers. Chassis shall be cost capped to €10m for the first 3 per season, Power Units at €15m and gearboxes to €5m. These teams will also have to use a spec telemetry system and Electronics system at €5m a year. So you could in theory have a Red Bull chassis with a Mercedes Power Unit and a Ferrari Gearbox and a McLaren electronics system.
The rules should be of such to encourage teams into the sport, but after a period of time, they shall be expected to make the leap from 'Team' to 'Constructor'.
However, this leaves a element that needs talked about, upgrades, how would these be policed and introduced is another topic.
Im against customer cars, but i can see them coming. I can see Haas being used as a Ferrari B team, ART being used as a McLaren B team, Toro Rosso will convert back to a Red Bull B team, leaving Mercedes to look to do the same with a new entry somewhere. That leaves 9 Constructors (Mercedes, Ferrari, Red Bull, Williams, McLaren, Sauber, Force India, Lotus & Manor) and 4 teams (Toro Rosso, Haas, ART, Mercedes-B).
However, another topic that needs to be looked at is the points system, the Drivers points would remain, but how would the constructors/teams titles be dished out? If you have a P9 for a team, does that P9 for the team go to the constructors P10? and the P10 Constructors point go the the P11? Points systems could get messy on the Constructors side quite quickly.
Lots of topics, lots of ideas from the way I'm looking at it.
If they do come in, the 'teams' need to come in with a year old power unit in a present/current chassis. A 'team' would need to be handicapped somewhere for taking a shortcut into F1 in my opinion, and arguably, the constructors need to be able to out-develop the 'teams' as the season goes along. The 'teams' need to b be able to access developments, but when they are allowed needs to be permitted to a specific window as well. These B teams need to be kept to strengthen and tighten the mid pack in the start of the year, but they need to drift to the end of the pack by the end of the year as the constructors will out develop them in a aero sense.
Thats my stand point.