Reb,
Zochim l’adom, one can acquire for someone else, even if one does not need for himself, BUT only if lo chav l’acherim, it does not cause damage/harm for others.”
There is no such concept as “Zochin” in this regard – it is not exactly hefeker that there are “kinyanim” etc. involved. It belongs to the shul i.e. to people as a whole – all are partners and whoever arrives to shul to use it . You have no “Baalus” in any sense other than actually using it.
See Shulchan Aruch YD 226:1 regarding the concept and ‘geder’ of a BHM”D that its really a shutfos, (See T”Z and Shach there.) consequently, it can only be “his” as long as he is ‘using it.
http://beta.hebrewbooks.org/tursa.aspx?a=yd_x6630
I am almost sure I saw Rav Cham K saying the above, but once again, it is difficult to rely on these Rav Chaim’s “M’pi haShmuah” psakim going around these days.