The most suitable option to fill in the blank space in the sentence "As [blank] of you that can come are welcome" is "many".

The word "many" indicates a large number or a significant portion of a group.

In this context, it suggests that a considerable number of people are welcome to come.

The sentence implies that there is an event or gathering where the speaker is inviting a group of individuals, and he is expressing his openness to having as many people as possible attend.