I don't see why they would be "Thracians" (Assuming we can even talk about Thracians in 1200 bc), the Philistines brought Mycenean pottery with them, and had a Cypro Minoan-like script, they most likely came from Cyprus and Cilicia, which had a mixed Aegean/Anatolian/Local Cypriot population, since most of Philistine pottery came or imitated Helladic pottery from those regions.
The links between the Aegean and Cyprus date back to the early bronze age with the Minoans giving Cypriots their script, which is similar to linear A but re-elaborated by the locals. We must not think of Cypriots as passive agents since they were among the most powerful bronze age kingdoms.
It is difficult to identify the precise ethnicity of the sea peoples' tribes, since as we can see from the few bronze age shipwrecks found, the ship crews were often mixed (Uluburun, Cape Gelydonia) and coincidentally the late bronze age was a time where many migration movements took place and the first time when Eastern Mediterraneans started trading with Central Mediterranean people on a daily basis.
Among the sea peoples invading the Levant there could have been, along with a majority of Aegean Greeks and Minoans, central Mediterraneans, AKA South Italians from Sicily, Sardinia, Apulia and Calabria, since imported and locally made pottery from those regions was found in Cyprus and the Levant in the layers of the sea peoples' invasions.
Remember that the Philistines were just one of the sea peoples, so while I think the Philistines in particular were Cypriots, as evident from their script, burial tradition, pottery and iconography (helmets and armor), the Ekwesh, Denyen, Lukka, Tursha, Tjekker, Shekelesh, Weshesh and Sherden were different ethnicities coming from many different lands.
The swords used by Sherden mercenaries have recently been compared with those used by the late bronze age Sicilians and South Italians by the archaeologists who are excavating the LBA South Italian sites.
South Italian swords have been often found in the Aegean in association with South Italian pottery and razors, and a Sicilian type sword has been found in the Cypriot wreck of Uluburun (near the Lycian coast), suggesting they were employed as mercenaries since 1350 bc by Aegeans and Eastern Mediterranean kingdoms.
The Naue II swords later found in Cyprus and the Levantine coast around 1300-1200 bc also are closest to the South Italian models.
No Bulgarian/Balkanian bronze age pottery has been found in the Levant to my knowledge, but only in Troy, suggesting that they invaded only Northen Anatolia, while Aegeans and their South Italian allies/mercenaries invaded the Levantine coast and Egypt.
Iconographicaly speaking the motifs in the sea people's ships depicted at Medinet Habu closely resemble the handles in South Italian bronze age pottery.
Damn, how long more we have to wait? Too eager to find out.
For some reason, I would think they're more related to Proto-Thracians who moved to the Aegean. At least they can relate more to this obscure, aggressive, and alcohol loving bunch, together with iron working.
Iron workers?
Iron working was practiced in the Near since 2,000 bc, especially in Anatolia, but only on a small scale, for really small blades and tiny objects like bracelets, Philistines didn't bring it with them, the sea peoples used bronze swords, iron working was already present in the Near East, and while the Philistines were among the first to mass produce iron, that happened when they were already settled in the Levant, and around the same time, or probably after the Phoenicians and other Levantine peoples did it.
They didn't have a prerogative, they mass produced it because other Levantine people started doing it too, not because they were already doing it before they settled in Palestine.
And by the way, the people who lived in the Balkans during the bronze age (who had nothing to do with the Philistines) didn't mass produce iron, they didn't even produce it on a small scale like Near Easterners did, to my knowledge.
Iron working was spread from East to West, not the other way around, there is evidence for Cypriots teaching local Central Mediterraneans how to smelt iron in the late bronze age.
"For unknown reasons, they migrated from that region to the Mediterranean coast near Gaza. Because of their maritime history, the Philistines are often associated with the “Sea Peoples.”
It seems it's the Egyptian texts (XIII°/XII°C.) which firstly associated the names of the 'Peleset' to the so called 'Sea People'. And later the name 'Peleset' was associated by some linguists to the 'Philistines'.
To be precise, the Peleset were mentioned several times by the Egyptians as an invading population, allied with many other tribes, some of those tribes (Ekwesh, Sherden, Shekelesh, Weshesh, Teresh) were given the epithet "of the sea" E.G: Ekwesh of the sea, Sherden of the sea, etc...
The Peleset in particular were not given this epithet, they were just listed as invading foreigners from the "north" along with these other peoples such as the Ekwesh, they allied with the Libu (Libyans) too in some occasions, they were very ethnically diverse groups of marauders from all over the Eastern (and probably central as well) Mediterranean coastline, the Philistines were just one of many other tribes hostile to the Egyptians.
They were never collectively known as "the sea peoples", they were known generally as "foreigners from the North/ countries from all over the North), the name of sea peoples was given by archaeologists because of the ephithets some of them were given.