If you can afford it, do the Savvy Mid-Arm now. You can run it with the stock shock locations but it limits travel.
Outboarding shocks allow you to run longer shocks which gives you more travel. The secondary advantage is having the shocks out at the end where they do their best work. Outboarding is good for short or mid-arm but not a requirement for either.
The advantage of the Mid-Arm is the geometry. It was designed with the 4" springs and 35" tires at the stock LJ wheelbase. Its on this platform where the Mid-Arm really shines. I've been told that the TJ doesn't take advantage like the LJ and believe that to be more related to wheelbase.
The Mid-Arm's "push angle" and "joint separation" is the geometry that makes it sing. The rear triangulation and the front 3-point suspension allows it to flex. Tire traction works better when the tire is on the ground.
I have Savvy Mid-Arm #001 as they used my Jeep to prototype the kit. It is based on Blaine's one-off (my words) suspension he was making for people using this-and-that components from different manufacturers. I was in line for one of those when they decided to finally make the Savvy Kit and used my Jeep to do it. Blaine did all the work, including the outboard rear shocks, taller front towers, rotating spring perches, etc, which is NOT part of the Mid-Arm kit. I already had Savvy's skids, lifts, steering, etc. Blaine added hydro assist later as well.
As others have said, and you are trying to do this on some sort of a budget, get the Savvy 4" short arm kit. You will use the same springs later and can sell the arms to offset your $$. Remember, with the Mid-Arm there is a lot of cutting and welding! There is no easy way back. The short arm works really really well. Yes the Mid-Arm is better, but don't half ass it! Do it right the first time!