several weeks ago, I promised to come back with some general thoughts about new vehicles. Sorry for the long delay - work piled up as usual. Wished I've had some more time and I'm afraid I still don't have enough for covering every single point or even any feedback to specific vehicles of your collection. So I gotta focus just on my major concerns when it comes to new vehicles: the integration into the rest of Onslaught vehicles, skill requirement and teamplay encouragement. I've had many more aspects and points in mind, actually. And even those three points I'm laying out below somehow still don't feel complemented for me. However, I think it's better to post at least this little bit I got now, instead of further phrasing other points. Nevertheless, I hope it's at least a start to be considered for any new vehicle which of course can be discussed or expanded later on and some ideas are even useful for your new Hovertank collection as well:
Integration into other Onslaught vehicles:
In my opinion, every vehicle has to fit to the rest of the pool. Not only regarding the visual appearance but mainly in terms of power. As we've seen over the years and especially at other communities recently, the vehicle fleet as an important Onslaught content is capable of splitting the community into two if powers are unequal. In particular, some representatives of the Gorz fleet are significantly higher powered than stock vehicles, thus very oftenly brushed off as overpowered. This is also why stock and Gorz vehicles hardly fit together and any mapper is somehow left alone chosing between them - for combining them wouldn't work out well. Anyway, to avoid this dilemma in future, my simple advice would be to make new vehicles fit to only one of those two classes.
Now, which one? Well, there's one major difference between stock and some of the Gorz vehicles: Stock vecs usually can't take out others by only one single shot. And even if so, the agility of the lighter vehicle (or even on-foot players) balanced it out to some extent. Take the extreme (as far as stock content is concerned) as an example: Goliaths vs. on-foot players: If only a little bit skilled, every on-foot player is able to succeed, he just has to observe the Goliath's slow cannon's motion, dodge its direction and land some hits. Same goes with any other stock content: you always have at least a bit of a chance to fight down the opponent. Point is, you always get involved into an interesting little battle if only for several seconds. That's completely different amongst overpowered vehicles: one shot and you're dead. The little battle joys like with stock stuff just don't take place. That said, it shoudn't be a surprise I'd strongly suggest to fit any new vehicle to stock ones in terms of power.
By the way, there'd be a very simple first approach to check power balance: Take a symmetric map, place a new vehicle on one side and any stock representative on the other one, have two similarly skilled players trying to get and hold an equally distant located node. If it ends up in extended back'n forth gameplay, it's a first hint the new vehicle is nicely balanced.
Other than power balance, new vehicles will be a nice and useful addition only when filling a real feature gap which other vehicles didn't cover yet. There's still plenty of room with regard to different anti-aircraft, artillery, stealth, shields, diving / air / terrain manoevrability, missile defence etc. capabilities. Fire modes are not the only starting point.
Skill requirement:
Partly due to pure power imbalance as laid out earlier, a vehicle's weaponry type in particular can also lead to another sort of issue, the "spamminess", which some custom vehicles are frequently and deservedly accused of as well. Broad splash damage or spreading multiple projectiles, goo bubbles or whatever in only a rough direction without requiring exact aiming hardly presume skills. Sitting fat-assed in a vehicle, eating a banana while playing the vehicle one-handed doesn't make it exactly interesting, neither for the driver nor for the opponent. So, for the gameplay's sake, any of these spammy weaponries should be avoided (if you ask me). When it comes down to an interesting and challenging gameplay, a driver has to be forced to aim his weapon(s) properly, plan both vehicle's and cannon's motions, be aware of and directly react to the environment (even on-foot-players, good power balance presumed), switch seats and weapons back & forth (if there's no gunner helping) in order to survive and succeed.
Teamplay encouragement:
Onslaught lives from teamplay and vehicles for that matter account for a major share of it in particular . Logically, especially if they are made for not only one player. Thus, one-seaters are somewhat alright, but two- or even multi-seaters are way better at that. Ideally, a fully manned multi-seater adds up to a more powerful vehicle than the same amount of players in comparable one-seaters. According to the oftenly quoted, pretty worn but still valid equation of "1+1 gives more than 2" in a team. Proven for instance by the good old Cicada, which always survives way longer when there's a skilled gunner accompanying the driver, using flares and secondary guns, occasionally helping at healing the vehicle, too.
Furthermore, one of the best and most popular ways to encourage teamplay is to have a vehicle capable of carrying passengers, like the Manta.
Bottom line of my suggestions is:
- Power should be equal to stock vehicles.
- Abilities should fill a gap other vehicles didn't cover yet.
- Weaponry should require good aiming or another kind of skill.
- Prefer multi-seaters over one-seaters.
- Enable passenger rides.
. [Most] UT games have been praised for a lot of things gameplay-wise during their time; if only their physics simulations were among those too... ah well, more bouncy cardboard box vecs for us.
. IMO, to take the time to develop a series of hover tanks only to see them casually humming around alongside every other custom vec in all the popular locales would be squandering part of their potential due to mapper shortsightedness. On the other hand, if ppl attempt to overcome this reality by creating new map versions with added water volumes across 'em, wouldn't that also be backwards logic, since you're creating a problem after you've coded the solution? I also couldn't help notice how fitting it was that the same person who rushed to include your first hover vehicle back then, the "Poltergeist" (also not an animal 
