The contract between a solicitor and his client is particular to each of them and the management company cannot claim that the conveyancing solicitor has any duty of care to the company. A new owner may tell you that his solicitor has said nothing about the contents of the deed or lease in regard to these matters, and that may have happened to one or two. It is most unlikely to have happened in all cases and most solicitors are quite diligent in telling their clients about such matters.
If the present arrangements work with two directors, why do you want more? It was Winston Churchill who said that the best committees were those of two people, one of whom was permanently absent. If you want to oblige somebody to become a director because of an obligation in a deed or lease, the company will have to take enforcement action which costs money, time and effort. If successful you gain a reluctant and possibly rebellious director. If your concern is that some people are not contributing their share of the costs, then you take straightforward recovery action, usually through the company’s solicitors.
It is not uncommon for residential management companies to fail to make their annual or accountancy returns, or to be unable to fill the offices of directors and secretary, resulting in fines from Companies House and eventual striking off of the company. That can have severe consequences in that there is no one responsible for maintaining the common parts and common services, and no one with the power to charge service charge funds for doing so. In such circumstances, it is not uncommon for properties to lose marketability and market value, and opportunities for speculative investors to buy at discounted prices with a view to turning a profit.
For so long as you own one of the flats I advise that it is in your best interest to keep this management going, despite apathy from most other people: once you sell and move away it will no longer be your problem and, yes, those who remain may well find themselves in a difficult position.