Brenno,
all that needs to be done is set a prizemoney ceiling on each class of race e.g. C0 winners of in excess of $80k ineligible, C1 winners of $100k ineligible, C2 winners of $150k ineliglible.
The horse will race as a C0 in a C3, still only take a country front but have to face much stiffer company in the C3 front and hopefully not go around at $1.04 stifling the betting as happens currently.
Not certain the prizemeney levels I have used as examples are entirely correct, but the structure would be an easy sell to participants and punters alike, the only one having a gripe might be the connections of the subject horse, but hey they already have had a good time and have cash in their pockets, they are now required to race horses that have more similar in ability as theirs.