Being a total idiot when it comes to LED lights and making them and all that, I've got a couple of questions for you. Can the LEDs function in a setup with high humidity? Like, if I had a tent or some kind of enclosed space with a humidifier in it, would they work or would I risk burning down the house? Annnnd, can you make ones that will work with T5 fixtures? Is that even a good idea or is it better to scrap those and start again with proper LED fixtures...?
First of all, one of the advantages for using LEDs is that you won't have to be afraid of them burning down your house! LEDs are light emmiting diodes, they light up if a voltage is passed through, and if they are blown up due to high heat or when their service time is up, the circuit is no longer complete hence there won't be any connection to continue. The LEDs last a long time if they are used properly, it is usually the driver or power supply module that die dirst. Similarly, once the circuit of the driver is blown (usually a capacitor on the PCB), the circuit disconnects. They are often enclosed inside some sort of housings as well.
To use in a high humidity environment, you might want to consider custom ordering a waterproofed design, which I can offer.
For an enclosed area, it is good to go with a lower power rating because even though LEDs are famous for being efficient, they would still emmit heat and you don't want to accumulate heat in an enclosed volume because it could affect not only the light but your plants as well. A common method to deal with this is to add a venting fan or temperature control system with cooler to allow fresh and cooler air to come in, keeping the temperature ideal.
It is harder to make one that works with T5 fixture because it is not only about the connectors but also fluorescents using a different voltage than LEDs. You will need to bypass the ballast and re-wire the fixture too. I'd recommend selling or donating the fixture and get a LED fixture.

Hope that helps, if you have more questions, feel free to let me know. If you want to describe your setup that needs lighting for a quote, you can send me a PM. Cheers!