but now we would like to switch it and possibily one day make that token tradable.
Why do you need to do that though? Is your company suffering from a lack of funds or something? From what I saw, most index tokens end up becoming worthless, so I doubt any big investors would buy your tokens. Even if you target the retail market, the question of why they would buy your token still remains. Not to mention, your index can be worthless if it just tracks your portfolio performance and you are the one who issues and burn the token, making it unreliable since you can just flood the market anytime you wanted to. Not to mention there are tons of similar tokens on the market with arguably bigger and more famous companies backing them.
I suggest looking for an alternative if the operational fund is your issue. Most small/medium projects that launch this token usually don't have any good reputation after they launch an index token since they end up worthless and illiquid. Offering a new tier of service or branching out to another investment service is probably a better idea, even if the execution is harder.