A i understand you sharing up to 90% of profit among token holders. But are you sure than rest 10% will be enough for keep exchange working (salary for staff, taxes, rent offices, servers etc. and some profit for oners) ? And how this dividends will be paid to token holders? Weekly or montly or quarterly?
That all teams have thought ahead even though they only hold 10% of tokens, if for other payments they may already have a reserve fund.