Custom designs in a MekWars setting

[Kobold]

So recently over at MMN there was a discussion about having a custom design contest.  This idea had come up at my home server (MekWars Forever) at one point as well.  Though both servers have very different set ups (MMN is a static 3025-ish setting, MW4E is set primarily during the clan invasion and advances through time), the same general concerns about "cheese" units were voiced in both cases.

Generally speaking, both servers (and most MW servers I am familiar with) balance forces by BV2.  When doing so, and when considering that at least one of these servers features clan v. clan, IS v. IS, and clan v. IS games, what are the biggest concerns when allowing custom mechs and using BV2 as a guideline?

(note that for the purposes of discussion, custom units would merely be added to the build tables, meaning there would be a random, low chance of acquiring one.  Merely adding the design doesn't guarantee people acquire the mech in large numbers)

[Zerberus]

Rule of thumb: Let the ones who designed a unit face it instead of giving them access to their own designs, and/or set up requirements which gear a unit for a certain faction may or may not use.

[Ferrosol]

general rules of thumb anything that mixes the following in large numbers is broken.  Clan mechs with speed  and  Clan Large Pulse Lasers and/or ERPPCs mechs with the above backed up by targeting computers. Examples of designs from canon I would consider overpowered are stuff like the Rifleman IIC or the supernova 3 or 4. Also in general I would ban anything that mountsjust one specific weapon whether that be a mech with nothing but mgs or northing but er ppcs or whatever.