Personally I doubt they will ever change FreePhoneLine again, apart from increasing the unlock key price.
It was an OK model for them way back, but now they have Fongo which obviously makes more sense to invest in.
I'm sure there is more than one high up person that would love to ditch FPL and send everyone over to Fongo

^^ All personal options
You probably know that Fongo Mobile has text features, albeit the short code side of it is a bit hit and miss. I have 3 different 'free text' apps to deal with the short codes from various companies.
It would be wonderful if we could get a reliable way to receive them through FPL even with paying for each one. But I can't see it happening.
It could be worth sending in a request through official channels though, you never know (
https://support.fongo.com/hc/en-us/requests/new). Support may not read all messages here, but they do read tickets.