Content - A Drac zombie Heavy/Assault 'mech would be swell. That's been my biggest complaint with that faction for a long while. So many glass cannons that can't hit the broad side of a barn once you get past that 60-ton mark.
Also, dialing back on the Advanced/Experimental technologies would be nice. Instead, simply having additional "Variants" of the new 'mechs that use TO rules would be nice. TRO 3085 is outstanding, don't get me wrong, but if I want to use anything with rules of a higher level than Tournament Rules (Like that spectacular-looking Orochi on pages 102-103), I have to lug my copy of TacOps to the LGS on top of my dice, rulebooks, maps, miniatures (in a massive Overlord minis bag), recordsheets, hexpacks, so on and forth. My bookbag is bursting at the seams and I weigh an additional 50 pounds* when I step out the front door. There is rarely that additional square inch of space to fit another core book.
This might sound like sacrilege to a lot of players, but I'd honestly like to see a brand new batch of 'mechs made for Succession Wars play. Say, a batch of designs made during the early succession wars? I think that with all the 3025-only people I run into (and myself sick and tired of that era after having to play in it almost exclusively since 2005), it would only make sense to make supplements that they'll actually buy, and something for guys like myself - for whom having to field the same old Jenners and Dragons over and over again gets dry. Plus, a new batch of introbox level 'mechs might make a good foundation for a future boxed set without falling back on artwork from 1985.
Writing
One thing I didn't like about TRO 3075's fluff text for the age of war section is the fluff for the Gladiator. I mean, the fluff itself was alright, but after being presented with these outstanding stats for a 'mech, to find out that the faction it's filed under pretty much never uses it felt like a raw deal. I would like to see more designs that are contracted to multiple factions. That's part of what made the unseen/phoenix mechs so versatile compared to, say, a Fafnir or Komodo. When it's a good design, but anyone can have it, it's popularity will certainly go up.
For the most part, I just breeze through the flavor text to find out who makes it and uses it.
Stats
I'd honestly like to see C-bill costs included in all of the TROs. I think that it feels more at home in a fluffier book like this.
Rules
I honestly prefer seeing rules left in the core rulebooks. The things already weigh a ton, and there's a wealth of options therein that haven't really been effectively explored with the canon designs, yet.
Art
A resounding YES to Mr. Iglecias, White, and Plog. Lewis, however... I'd rather he be removed from TRO duty. I'm sure he's a great guy, but I find his art to be bland and lacks detail - and when you're drawing stuff that's going to be sculpted, effectively making it the face of the franchise, you can't afford to have unappealing designs.
On the topic of my prior mention of making a TRO for the early succession wars, if we could get Loose to do some industrial design inspired 'mechs again, it would be a fantastic nostalgia trip. Some people might speak ill of his artwork, but I, for one, loved the heck out of TROs 3025 and 3058.
Layout -
I think that rather than having deployment listed purely in text format, a quick-glance section on each page showing which factions each design is available to (Using faction logos, most likely) would make this game a lot more approachable for new players.
*This is not an exaggeration. I did a before/after with my bathroom scale.