Without detracting from or disagreeing with the many great answers already given, this one is more of an "information systems management" than a "risk model" problem. It's a classic "should I bespoke, outsource, or off-the-shelf?" dilemma.
So then the question becomes whether and/or how the risk you want to model differs from that of the modal/median customer of the mainstream providers. If you were yet another mutual fund tracking the same benchmark as the other thousands of mutual funds, there's almost no discernible reason to measure your risk differently from them if you manage it the same way, in a simple competitive arena. Sure, you might have some house difference to the median that is your "secret sauce". But to measure the sauciness of that secret sauce, it helps to compare yourself to the competition in their/the-classic terms. That's how you're differentiating!
But if say you were an equity investor whose core focuses were say REITs and/or private equity investor, then it might be perfectly rational to say that the cookie-cutter models for the stock and sector jockeys were not fit for your purposes.
The grey area lies, eg, where you have a "growth" or a "value" investor who is a classic equity investor; but has a very different view about what those terms means to the canned logic of the off-the-shelf solutions. The models might tell them they have X style exposure; but the investor measures it themself in a very different way. Then they need their own risk model, suited to their method/prejudices, because they are not operating just to beat thousands of other lookalikes with the same frameworks (that validate the same models as the lowest cost solution).