I want relevant objectives, too, but respawns have the following problems in my mind: they...
1. Ignore the real problem.
A gamemode like King of the Hill is going to stay Skirmish - even with respawns - as long as the objective is in one place. This is because of player behavior. Some people just want to kill. QP is the queue for slap-dash lone wolf teams who don't necessarily share a goal, and for many people, their goal is killing. That's just the nature of gaming.
We already have respawns in CW; it didn't fix much, because the maps and objectives were poorly designed and promoted deathballing themselves. I really don't see how this will change with or without respawns.
2. Reduce earnings
Matches with respawns will take longer. Unless rewards increase accordingly, the time-to-earnings ratio will increase and players won't be earning as much. And if you're going to increase earnings, why not just do that from the outset? Good way to incentivize objectives.
3. Increase the meta gap
Respawns turn the game into an attrition match in which damage output becomes even more important. Which means that players will be more encouraged to take "meta mechs", i.e. heavy damage dealers, and will move even further away from lighter mechs, bracketed builds, or role players, because they won't let a player keep up with the attrition game. Respawns would be bad for balance.
4. Promote careless behavior.
I know AUSwarrior24, He of the Great Respawn Campaign Leadership
, and some others are sick of hearing this argument, but I don't see how it's wrong. Respawns will cause players to devalue their durability. Specifically it will make games an attrition battle, which will cause players who lose an arm to suicide, and rightfully so - it's inefficient to your team's goals to continue with a sub-optimal mech. The lack of respawns is what contributes to players' willingness to keep fighting with damaged limbs, which is a huge part of the game and of Battletech.
With damage impossible to eliminate, suiciding would simply become the optimal strategy. You already see a little of this in FP, though not much because respawns are limited to four and FP is inhabited mostly by smart teams. Toss respawns into the Tier 6 Potatolord Pool of Quick Play, and I'll bet money that you'd see a lot more suiciding.
I want relevant objectives too, but I'd prefer to use the carrot and not the stick.
If you want to make objectives relevant, give them an impact that players will care about.
The most obvious way to do this is to make objectives relevant to killing; if you don't do the objectives, killing gets harder. Plenty of creative ways to do that - ECM towers that make it easier to find the enemy, landing zones that drop you off closer to map center, capturable artillery emplacements. Be creative. Be interconnected. Don't just throw in abstract features like respawns, that's every bit as much a band-aid as Ghost Heat, doesn't actually fix much, and introduces new problems. It's bad game design IMO.