I started on Orions with the plan of using the VA as a Std engine SRM/LL Brawler... and it sucked horribly. I went through several configurations and hated pretty much all of them. I ended up mostly leveling it with LRM50, TAG, ML, and it does rather well. Reasonable speed, lots of ammo, alternating LRM25 in single waves with 15/10 tubes on each arm. But it was horribly defenseless up close, and you can't always rely on a team to protect you in PUGs. I ended up with LRM30, 2xSSRM, 2xERLL, ad it works beatifully.
For the K, I went straight to the typical CTF-3D Brawler loadout, AC20, 4xML, but found it to be horrible without the 3D's mobility. I immediately dropped that and began trying various combinations, trying every ballistic, sometimes different missiles. In the end I decided to try something I've never been satisfied with on other chassis, 4xLL. It's a beautiful thing. I find it to be the perfect mech for the loadout, with just the right balance of speed, armor and tonnage to pack heat sinks into.
I had the most trouble with the V. I went through a ton of configurations and nothing was good. 2xAC2s were too hot. 2xUAC was too heavy and unreliable. I hated it with a passion. The only one I considered close to playable was 2xAC5, 2xLL, 3xLRM5 (I actually really like the 3xLRM5 as a fast-firing, CT coring, assist-scoring, Light-chasing machine). I ran the 2xPPC, AC10 for a while and got some decent scores with it, but didn't really like it. I had pretty much consigned the mech to be sold off. Then I decided to go with something simple, toss out all the variant-specific advantages, and loaded AC20/2xERLL and it all came together. I'm not sure why, but it just works. In fact it works considerably better than my nearly identical Victor, which is slightly faster, with more armor and JJs!
In the end I went from greatly disliking the entire chassis to enjoying it immensely, and all 3 variants are among the most successful mechs I've piloted to date, stat-wise.
I still think it's ugly, though.