FWL is playable without the Juliano. It's just we become significantly better with it.
Before then, its general mission role is filled poorly by the T-IT-N11M Grand Titan and T-IT-N10M Grand Titan but we have few other options. Thus we do better to run the MR-5M as our main assault, backed by AWS-9M or AWS-9Ma. The Trebaruna is fairly good too, though it needs protection to do well.
The Juliano is basically an implicit admission that a 'combat effective' range of 6 hexes on a 4/6/* unit is no longer acceptable in 3150, and that our primary Grand Titan was no longer getting the job done... nor was our Stalker. The Juliano increased the effective combat range, while also increasing damage output. While it's weak to high-speed 'slasher' units, this is not a problem since its lancemates and the Kopis Battle Armor can usually counter them in return.
Nonetheless, we can win without it. We started winning once our medium corps became more noted for its SKW-2F Shockwaves and so on instead of SHD-7M and GRF-5M. "Hurr hurr toss light gauss on it" was what was ruining us as a faction, and the developers finally got over it in TRO 3085. We didn't even need great Mechs, we just needed 'not irresponsibly stupid, unplayably bad trash that makes it clear the folks at FASA did not like us and wanted us to stop buying their product so they could focus more on the davions and steiners and clans.'
We got it. The FWL became much more fun almost overnight due to it. The Juliano is just an example of making us finally scary in some contexts, instead of just 'playable.'