If I read you correctly, you are fishing for plot hooks, to make a saga revolving around an emerging portal project ...
One possibility is the faction who oppose the peculiarities of the Hibernian Peripheral Code, and who would like to see Hibernia better integrated with other tribunals, and maybe remerge her with Stonehenge. This intrigue has been ongoing for the better part of a century, but most magi who have been sent to investigate appear to blend into Hibernian customs, such as Lugardis of Elk's Run. Establishing a portal could enable a mission which remains part of a continental or English community. It may be a little too old-school Tremerian for some troupes, but certainly a playable plot for those interested. Funding should not be an issue, if the Tremere and the Quaesitores take interest.
A second obvious option would be a clique of very scholarly magi, who want to get the best of both worlds: both the vis sources of Hibernia and the correspondence and book trade of the continent.
What is plausible is entirely a question of how you want the infrastructure and economics of your saga to work. RAW explicitly leaves this to troupe decision. IIUC, the portals between Durenmar and the Domus Magnae are open to all, at 2pvf/magus. The portals to Harco OTOH are left much more to the discretion of the guardian and/or the SG. There are several such portals, but not clear than anybody but redcaps can use them.
New portals are not just a question of paying the cost including fair salaries to the few magi who are able to do the enchantments. House Mercere owns the portal and instates a guardian who is responsible, not only to prevent unwanted elements from using it, but also prevent anyone, even friendly magi, from studying the portal to be able to recreate the enchantment. Suitable guardians are rare, and there is nothing to say that House Mercere will allow a portal even if the tribunal unanimously decide that they want one. Again, there is no universal canon answer to whether it should be possible, but if it suits your plot, all you need is to design a perfect guardian, be they a covenant or a faerie queen ..