This is a good idea but needs refinement.

Every rep system can be gamed in an anonymous system with sybil attacks so long as providers can remain anonymous. The thing here is to strip anonymity in such a way that it grants no hiding power.

Therefore the most straight forward system would be one where it is hard to earn and easy to lose.

Take for example a trader who's providing liquidity on one or two specific markets, but consistently provides deep liquidity and doesn't front run, put in ghost orders or pull orders very often. This person is a specialist and should gain rep by number of days and % of liquidity he/she is providing. The more liquidity you provide the better your rep.

But what if they were playing a long con? Well this actually becomes solvable by capping the max rep to some value and disproportionately impacting it for bad behavior. First screw up is a 99% hit to reputation. You're back to square one and this doesn't go away ever. It has to be earned back and the only way you earn it is by providing deep liquidity for long periods of time. I'm not talking minutes or hours here. I'm talking weeks.
Say every week you provide liquidity you get 1 point for every % of a given market you've made. Cap that at 100 and let all noobs start at 1.

An even better system might be like the system in certain MMORPGs for leveling up. Every level increase requires some power law accumulation of points. For example level 1 is the starting point. Gain level two with two days of making liquidity of at least 1% on a market. From there you need 2x as much to gain another level, i.e. 4 days then 8 then 16, 32, 64, 128, 256, 512 etc. These would translate into low numbers like 1,2,3,4,5,6 in order to make it really painful and expensive to game the system.