Goldbishop, I'm not sure i agree with you regarding how to handle it.
For one, that approach doesn't really address the main issue, of how the clan forces fight, which is the main part of zel. 'what they fight with' is not a big part. Especially since as the invasion era moved forward, the clans often stopped making bidding a big thing, but they still mostly stuck to their semi-dueling fighting style.
Plus, the method you described leaves the clan player as having substantially more force than the IS player, which is unfair, not to mention having those extras hanging over their head like the sword of damocles would feel like they are going to be punished for using the very tactics that play to the inner sphere's strengths and actually might let them win. It also would reward a player that plays the clans as tactically inept trolls, by letting them drop in an easy victory by goading the is player with easy ganging up oppertunities.
In short, reinforcing most of the bad stereotypes about clan players.
Mynsuggestion for handling bidding, which btw is more of a scenario thing than a zell thing, is to draw up even pointed forces as normal, but then have the clan player bid against a 3rd party (a gm or someone that isn't their opponent) with the bids consisting of which units from that force they will actually be putting on the table, the unbid units put into reserve.
For zel itself, decide how strict you want to be, and decide what actions break zel. Reference the standard BT stuff for this if it helps. Make a list of these actions for reference.
Then get some beads or other tokens, and set aside a 'honor pool' off to the side for them.
During the game, if a IS player does one of the zell breaking actions, stick a bead in the pool. If the clan player does one, take a bead out.
Before the game, decide how many beads it will take to bring in the reserve units. I'd suggest doing it on a per unit basis, rather than an all or nothing, but if there are easy groupings like stars or whatever, feel free to use them.
The idea here is that the clan player has chosen to play ar a handicap by usin only a percentage of their equal value force. Even if the IS player completely ignores zell and racks up the honor pool fast, it remains an even fight between the players. If both sides stick to zell, the clan player has the tactical challenge of dealing with the IS side's greater survivability against attrition, but it still will be a mostly even fight between the actively engaged forces. ESpecially if the clan player uses the option to challenge multiple units.
If it helps keep track of the various 'duels' just get some colored and/or numbered chits, and put matching chits on the bases of the units on each duel. And then just forgo the vocal challenge aspect and treat opening fire on a target as the challenge. This has precedence in the novels (where vocal challenges were usually only for special battles), plus it isn't like units in AS can split fire easily.
If bidding was not really involved in the scenario (like some of the stuff that happened in the fedcom civil war era, or during tukayyid, then instead of being able to call in reserve forces allow the honor pool to buy things like dice rerolls, though in those scenarios it is likely there would be fewer actions that count as breaking zell, in the first place.
