The promo states: "Exclusive custom 'Founder's BattleMech'" which makes it sound as if you're getting another Mech on top of the one they are giving all players.
I would be very interested in knowing if it's just a modification to the free Mech everyone gets, or if it is a unique Mech in and of itself.
This was my understanding, too, with the EFP the player who purchases it will obtain an extra mech that is equipped with a C-bill booster, and once the game is launched officially, anyone will be able to purchase any of the mechs that the developers introduced up to that point, so that the EFP users would be provided with the same choice of mech as everyone else but will in addition the would also possess the EFP mech (thus, I do not see any reason for complaints regarding the randomization approach as they will eventually get their favourite mech type anyway, just a little bit later at the official MWO start).
What is the point then for paying $60 for the EFP? Is it just for those who wish to start a bit earlier with playing MWO and get this C-bill booster on top of it, but being limited to only 4 mech types to choose from at the same time and not having the possibility to choose one of the mechs available at MWO lauch then (unless one is raking a lot of C-bills with the EFP mech until the offical MWO start or uses the additional 80$ for online items' purchases also included in the EFP). Such an option will most likely not appeal to me and offers relatively little advantage over the of Veteran Founder's Package (VFP) then, but after reading the description of 'Operation Inception' it is completely possible that the differences between EFP and VFP are just the C-bill booster, twice as much online purchase cash and one month more of premium account.
I am not certain that all the mechs announced by the developers so far will not be available at the offical MWO launch. At least the availability of all those advertised mech models is what I would expect (also providing the necessary diversity for the game start and not just 4 models, plus variants/modifcations, in total). If only one mech representative for each weight category will be available at the official MWO start, possibly, a lot of users here will be disappointed of the developers (from being wettened in their appetites with new mech models introduced every two to three weeks, but when it finally comes to delivery none of these would be made available at game start). As a consequence thereof, some may decide to wait and not participate until the game becomes more complex and diverse then (not really helping the development/popularity of MWO) or it may not be mid- to long-term motivating due to a lack of options (also depending on other factors, of course, such as maps/environments, game modes, etc.) and BattleTech/MechWarrior newcomers will not be awfully impressed by a selection of only 4 different mech types at game launch, even if it is F2P.
In my opinion/estimation the whole Founder's package business has not been figured out well by the developers to date, but it will surely be a good option for them to also collect more cash later on at the start of the Clan invasion (possibly, calling them 'Elite Trueborn Packages' or 'Elite Bloodname Packages' then).