Is there a way to get the Italians to colonize Tunisia instead of the French? If so what effect would it have had on Italy, emigration, and the economy? As part of this Italy gets its OTL empire in addition to Tunisia. Can it hold it and make it essentially part of Italy, more so than Algeria was part of France?
Well by 1881 there were already a sizeble italian community in Tunisia and frankly was considered a de facto protectorate/colony by Rome thanks to the heavy investment and privilege both economic and diplomatic enjoied by the italians...so the problem is not get Tunisa but keep it.
Maybe at the Berlin congress of 1878, Italy don't remain isolated and accept as compensation for the Austrian occupation of Bosnia a formal aquisition of Tunisia.
If this happen some compensation for France will be needed (some economic reassurance regarding their interest in Tunisia and probably Libya will be occupied by the French) and some reassurance towards the British regarding the straits.
If Tunisia remain/become Italian, well economically it will be a very good things...in OTL the French occupation and the nullification of the italian economic interest were a severe blow and frankly the land is the perfect settler colony for Italy so if Libya got a high numbers of colonist, image a place much more confortable.
The things is that the hand is played well enough an alliance with France is possible or at least butterfling Crispi and is rabid Francophopia (that have in the 'Slap of Tunisi' a great ground for grown nationally) who caused a disastrous commercial war between Italy and France...and was one of the great cause of the mass emigration of the time.
Even if things goes as OTL regarding the relationships between Italy and France, after that is probable that Rome will sign the Alliance with Germany and Austria from the start in 1879 due to the added pressure